Hands free auto repeat. Hidden feature or stuck key?
Rather than an exorcist, I'd take it to an Apple Store, because the keys should not repeat unless you let them pressed. There are various factors than can cause this behavior, but if the machine is relatively new, there shouldn't be any reason for this to happen. Most of the ideas come from a Software malfunction, some utility misbehaving or such. 

I suggest you create a new user and work a few hours/days from there to see if it happens again. If it never happens, migrate your data to this new account and problem fixed. If it keeps happening, rush it to an appstore and see what happens. It's not common. Good luck!