s long as he eats at minimum 8-12 times in 24 hrs, the rest is normal. There is a huge range of normal behavior for newborns & nursing.
II think what you are getting is the newborn boobie drunk pass out. Try removing clothing, keeping him awake to finish, etc...but it may not work, never did with mine.
& it will help you understand WHY it is happening, but it won't change anything,. It is from a hormone called CCK that aids in digestion, but it also makes some tiny ones very very sleepy.