Bought Apple Watch set it up was exercising everything going well, just walking so not strenuous, ten min walk to try it out, wore for maybe hour, took off went to bed, laid on left side, was in bed for roughly 5 mins, and body like shifted jerked, no pain no other sensation, instantly knew it was to do with that I watch! As this has never happened, I have immune suppressed body ( taking prednisone) Anyone know of this happening,