Newborn grunts all night

Mi

My newborn grunts for hours until he is asleep. It usually begins after we feed and burp him and lay him down for bed. He will lay there and grunt until he puts himself to sleep. He will also wake himself up to grunt but then go back to sleep. Some of it may be pooping but I know he isn’t pooping for hours. Is it reflux or just regular baby noises? He isn’t in any distress when he does it - he looks very content as he grunts.