My 15 week old baby has been waking up frequently during the night like every hour or two. why?nothing has changed, she eats ,nap and play fine.help

Frequent waking: Babies are known to have growth spurts and often will want to feed more during this time. Hopefully she will return to her usual schedule soon. If not try to stretch the time before you intervene by 15-30 minutes at a time. Make sure her surroundings and noise exposure haven't changed. All the best.

Sleep consolidation: occurs from 1-4 mos. At a consistent bedtime, feed her, wipe out her mouth with a soft cloth, read & croon in low light. When she's drowsy, but awake, put her in her crib in her room without a bottle or pacifier. She'll learn to self-calm to sleep. 5-mo. olds have implicit memory, which leads to learned behaviors at 6 mos., when babies who can self-calm will go back to sleep when they night-wake.