In my sleep I grind my teeth

UK indie-rock fans of a certain age will be have Therapy?’s “Teethgrinder” in their heads right now, but this isn’t an indie-rock thing. It’s a weird health thing.

I appreciate this is a long shot, but does anybody have any idea why I might be tensing up like crazy whenever I go to sleep? I keep waking up and my arms are pushing with all their might against the mattress or, if I’m on my back, my hands are trying to push themselves through my ribs and into my chest cavity. It certainly isn’t deliberate, I’ve no idea why I do it, and I’m pretty sure it’s  ruining my sleep and exascerbating the carpal tunnel syndrome-a-like symptoms I’m getting in my hands.

More to the point, does anybody know how I can stop it?