If you are worried about it doesn't do any harm to talk to the doctor next time you're there.

I would say it's normal though. Watched DS last night and he does the same thing, thought it was just his Daddy. But nope they both do it.

Spoke to my mum today she said I did it as a kid although I dont know if I do it now, obviously I'm asleep lol DH is always asleep first so he can't tell me.

Oh and 2 out of 3 of my sisters kids do it.