Hearing for baby. As a parent your ears are sensitized to every little noise your baby makes, and babies are noisy sleepers. So its normal that while your little one may fall asleep nursing, you may be wide awake in bed listening to every sound and wondering if they are sleeping well. Couple tips- turn down the monitor or don't use one in a small house. Try to relax knowing your baby is well fed and sleeping.
Can be a few things. There can be many reasons for this, but in general it has to do with the baby being a baby... In other words, the baby was used to the environment of your stomach for nine months. Now, the baby is out and is confused and not sure how to calm and sleep without those feelings again. You may notice the baby sleeps while held. Holding, rocking, pacifier use, white noises, calm and quiet all help.