L.L.
Hi,
I have a 4 month old girl who is on the same schedule, only I'm feeding her when she wakes at 3 a.m. She's starving at that time, takes 6 oz in a flash, then goes back to sleep until 6 or 7. I would definitely say he's probably just hungry, even if he's not necessarily crying. My daughter does the same...she starts kind of thrashing around in her sleep so I quickly feed her before she starts crying. (don't want her to wake my toddler up.)
They're growing so quickly that it's hard to just expect him to sleep thru the night at this point without getting hungry. I bet that's what it is.
Good luck,
Lynsey