My guy is about 8 or 9 mos and the head swaying thing he does whenever he has his head unsupported by more than a few inches. At least it doesn't have anything to do with feeding. Its not like he shakes and he can periscope just fine. But, when hes trying to bridge a gap or he's looking around from some awkward angle he sways. Its sort of a random sway - looks very ungraceful.

Yea, the second is what I thought. He yawns alot so maybe he's got a loose jaw.