My DS 9mo sometimes shakes/rocks his head from side to side when he's trying to fall asleep.
Sometimes I try and hold it still, or stroke his head to get him to stop. I don't know whether to intervene or not. Often he goes to sleep without me in the room so guess he manages without me interfering.
I just worry its not good for his neck/head or that it might be his ears/teeth bothering him.