Do you take any medication at night? That would be my first thought. People sometimes sleepwalk, you might have to put some type of pressure sensitive alarm on your bed that will wake you up if you get out of bed asleep. Definitely let your doctor know you are doing this.
I woke up in the middle of night,wasn't fully awake,I took my mobile (which I put on the desk near my bed) and bit it so hard that the camera broke off inside my mouth! what's the problem?I sleptwalk once or twice but that was years ago.