Head movements?

Hey, this is really weird but I thought I'd ask incase anyone gets anything similiar.
Sometimes my head just seems to move involuntary, it's like a jerk. Does anyone else get this? It's not noticeable and it's not like a twitch, it's just me who feels it. I always worry that my brain is banging against my skull, lol. It's a bit scarey actually.
I wonder if it's because I tense my neck muscles or hold myself stiffly, anyone have any ideas?
Thanks.

Absolutely tension.I have the weirdest feeling and sensations and from holding my head at certain angles when im really tense and geez yes I feel like I can feel my brain in my head most of the time and yes the jerks are your muscles responding to tension and the release of same causes jerks or spasms.. So don't worry be happy its all good.Relax and it will just go away .. but its normal