K.R.
He is newly out of your tummy, and is used to constant motion and noise during the day. Try a vibrating bouncy seat, a baby swing (designed for newborns - if he is too upright his head can flop down and it can restrict his breathing) - or better yet, put him in a wrap (moby wrap, maya wrap...) and carry him around with you - your warmth, your voice, your heartbeat, and your smell along with the motion he is used to will soothe him right to sleep! I found with my babies that if I wore them for about 20 minutes after they fell asleep they would be REALLY crashed out, and then I could untie my wrap and lay them in their cradle with it and they would stay asleep for a while.