Make him naked while he feeds or take off socks dont let him be totally comfy while he feeds or he'll keep sleeping
believe me, if he was hungry he would be awake to eat. when i was at the hospital they make me wake him every 2 hours to eat, he was not hungry and would cry, than just fall asleep. i got home and we are on a schedule of ever 3.5 to 5 hours. and he goes right to town, falls asleep at the end, and is content.
i would monitor him during the day, and see when he starts to fuss to eat. see when he is saying he is hungry and not get to caught up on the 4 hour rule. especially if he is gaining weight and his diapers are all good. 3-4 poop and 3-4 wet ones every day. i think that is a better judge than generic guidelines.
You can try to press ur boobs so that the flow of milk into his mouth will keep him alert.
Is he jaundiced? That makes them sleep a lot more
I think he was not hungry. In this case, don't feed him when he will feel hungry feed him.
My daughter is a Lil over 2 weeks I time her for every two hours if not she sleeps. She falls asleep instantly as well. So I start feeding then when she falls asleep I change her she wakes I start feeding, when she falls asleep I lay her down if she's still hungry she'll wake. She's hard to feed sleeping so well. My first would wake every 1 or so.