I used to take off at great speeds when in a state between waking and sleep. Used to terrify the heck out of me because I couldn't break out of it, or at least not without great difficulty.
I once sensed a fire in the state you describe. It was nothing but a lamp (no fire), but the reflex was ungodly. One giant leap across the room from lying dead flat... it took the heavy covers with me and I slammed into the wall. I felt like a total ninja.. I could never repeat it now.
(I am much more certain of this story than my "floating in mid-air" theory.)