Could be inner ear connected - pure coincidence, I would guess. The next time this happens (unless lying down) try yanking, and I mean really sharply and abruptly, your head up/back as far as you comfortably can - do it sharply/quickly without fade-in/fade-out (if you see what I mean - as if hit in the face and stopping on a headrest). If the sensation disappears then it is very likely the crystals in your inner ear that are shifting about. I had this crop up intermittently over maybe 3 years but in the last year increasingly rarely, and now (touching wood) it has not happened for many months. It was decidedly disconcerting the first few times, read up on possibilities and tried the above - perfect result, mind completely at rest from there.