Also ссылка Babies cannot choke if they are laying on their back.

Buy a crib wedge. For now, you can roll up a receiving blanket and stick it under the crib mattress under his head. It is most likely reflux, so I would also schedule an appt with your pediatrician.

my son did it for a few days after he was born then it stopped. take him to the doctor though just to make sure it not a bigger problem

I recommend getting him seen asap just to be safe