Reason why I wondered about his teeth is because, I remember reading that teeth can cause unusual/strange head 'behaviors'.
He's chewing ok and eating faster now though. His neck isn't stiff. He just doesn't want to drop his head. Well actually he will but then picks it back up. If it had been while he was so acute I would really be concerned but I'm thinking he may just be a little stuffed up. I'm gonna run it by my vet anyway.
Usually when their teeth need floating, they'll hold their head cocked to one side or the other.