Babies toss and turn all night because they spend roughly half their sleep time in a light, active sleep stage where movement is completely normal. Newborns split their sleep almost equally between active (REM) and quiet (non-REM) sleep, compared to adults who spend only about 20-25% of the night in REM. During active sleep, babies twitch, squirm, flail their arms, make faces, and shift positions. This looks alarming, but it’s a sign of healthy brain development, not a sleep problem.
That said, not all nighttime restlessness is just normal sleep cycling. Several fixable issues, from room temperature to teething to digestive discomfort, can turn ordinary movement into genuinely disrupted sleep. Here’s how to tell the difference and what you can do about it.
Active Sleep Looks More Dramatic Than It Is
Infant sleep cycles are much shorter than adult ones. Where an adult cycles through light and deep sleep stages over about 90 minutes, a baby’s full cycle lasts closer to 50 minutes. That means your baby transitions between sleep stages more frequently, and each transition is a moment when movement, brief waking, or fussing can happen. Multiply that across a full night and you get a baby who seems to never hold still.
During active sleep specifically, babies grunt, jerk their limbs, move their eyes under closed lids, and sometimes even cry briefly without fully waking. Their breathing may be irregular. Parents often interpret this as distress, but if your baby settles back down without intervention, they were likely never truly awake. Picking them up during these moments can actually interrupt a sleep cycle they would have completed on their own.
Sleep Regressions and Developmental Leaps
If your baby was sleeping relatively well and suddenly starts tossing constantly, you’re likely in a sleep regression. These tend to cluster around 4 months, 8 to 10 months, 12 months, and 18 months, though every baby’s timeline varies. Each regression coincides with a burst of brain development: learning to roll over, pulling to stand, language processing, or new awareness of separation from you.
The 4-month regression is especially noticeable because it marks a permanent shift in sleep architecture. Before this point, babies essentially have two sleep stages. Around 4 months, their brains reorganize into the four-stage adult pattern. This reorganization means more transitions between stages, more opportunities to partially wake, and more movement as their body adjusts. The good news is that each regression typically lasts two to six weeks and resolves on its own as the new skill or brain change consolidates.
Room Temperature and Overheating
Babies who are too warm toss and turn significantly more. The AAP warns that overheating increases the risk of SIDS and recommends dressing your baby in just one more layer than you’d wear comfortably in the same room. Signs of overheating include sweating, a hot chest, and flushed skin. Skip hats indoors once you’re home from the hospital.
A practical way to manage this is by using a sleep sack with an appropriate warmth rating (measured in TOG). For a room between 68°F and 75°F, a 1.0 TOG sleep sack is typically right. Warmer rooms (75°F to 81°F) call for a lighter 0.2 TOG sack, while cooler rooms (61°F to 68°F) may need a 2.5 TOG. If your baby is kicking, arching, or constantly shifting and you can feel warmth or dampness on their chest or back of their neck, try dialing back a layer before assuming something else is wrong.
Teething Pain
Teething is one of the most common reasons an otherwise good sleeper suddenly becomes restless. Most babies start teething between 4 and 7 months, which conveniently overlaps with several sleep regressions, making it hard to pin down the cause. Clues that point to teething include excessive drooling during the day, rubbing objects against their gums, crankiness after eating, and more irritability than usual.
Teething discomfort tends to be worst in the evening and at night, when there are fewer distractions. You might notice your baby chewing on their hands, fussing at intervals, or waking more frequently than usual. The worst of the pain from a single tooth usually lasts only a few days around the time it breaks through the gum, though the process repeats with each new tooth over the next couple of years.
Gas, Reflux, and Digestive Discomfort
Digestive issues cause a specific kind of nighttime movement that looks different from normal tossing. Babies with gas or reflux tend to pull their knees up toward their chest, arch their back (especially during or right after feeding), and seem unable to find a comfortable position. Crying that escalates after lying flat is another giveaway.
Reflux is common in infants because the muscle between the stomach and esophagus is still maturing. Stomach contents flow back up more easily when a baby is horizontal, which is why nighttime can be especially rough. If your baby spits up frequently, seems uncomfortable after eating, and arches during or after feeds, reflux may be contributing to the restless nights. Most babies outgrow reflux by 12 to 18 months as that muscle strengthens.
Eczema and Skin Irritation
This one is often overlooked. Babies with eczema or other skin conditions can spend 5% to 14% of their sleep time making scratching movements, and the itching is typically worse at night. Research using infrared monitoring of sleeping children with eczema found significantly more limb movements even during deep sleep stages compared to children without skin issues. The result is fragmented sleep, longer time falling asleep, and lower overall sleep quality.
Scratching movements happen most during lighter sleep stages, which babies already spend a lot of time in. If your baby has dry, rough, or red patches on their skin and seems to toss more on nights when their skin looks worse, managing the eczema itself (through moisturizing routines and appropriate skin care) can directly improve sleep. The connection between eczema severity and sleep disruption is well established: worse flares mean worse nights.
When Restless Sleep Is More Than Normal
There is a recognized condition called Restless Sleep Disorder, defined by five or more large body movements per hour of sleep, occurring at least three times a week for three months or longer, with noticeable daytime consequences like fatigue or behavioral issues. However, current diagnostic criteria apply to children ages 6 to 18, not infants. For babies under a year, the vast majority of nighttime tossing falls squarely within the range of normal development.
Patterns worth bringing up with your pediatrician include consistent difficulty breathing during sleep (snoring, gasping, or long pauses between breaths), failing to gain weight appropriately, or sleep that seems so disrupted your baby is excessively drowsy or irritable throughout the entire day with no improvement over weeks. These can point to conditions like sleep apnea or food sensitivities that benefit from evaluation.
Practical Steps to Reduce Nighttime Restlessness
Start with the environment. Keep the room comfortably cool, dress your baby in one layer more than you’d wear, and check their chest for warmth or sweat before adding blankets or thicker sleepwear. White noise can help smooth the transitions between sleep cycles that cause partial waking and movement.
Give your baby a moment before responding to nighttime movement. Many of the squirms, grunts, and brief cries happen during active sleep and resolve without your help. Waiting 30 to 60 seconds lets you distinguish between a baby who is cycling through a sleep stage and one who is genuinely awake and uncomfortable.
If you suspect a physical cause, work through the most common culprits one at a time. Check for teething signs during the day. Watch for the arching and post-feed fussiness that suggest reflux. Examine their skin for rough or inflamed patches. Each of these has a different solution, and identifying the right one can turn a miserable night into a merely noisy one, which for babies is perfectly fine.