sudden trance

[akwalpurgisnacht]

So, sometimes, after doing something especially kinesthetic in the past couple of days, like swimming, flying or jumping on a trampoline, I will feel the sensations of those things while lying in bed trying to sleep.

Today, as I was listening to EMG's induction, I felt as though the mattress under me was moving ; like waves; a very good example of the sorts of sensation I get after having gone swimming.

then, later, I was lying in bed trying to recapture the sensation. I felt the matress moving under me. I then decided I would try and visualise one of my favorite mental spaces: the void of interstellar space; with the stars all around. Being in a half-dream state, I could not of course just be there; I had to travel there, so I imagined flying up; but it was too slow, and so I imagined that I would catch a ride on an airplane to the upper atmosphere.

I grabbed onto the tailfin of my imaginary boeing;

and very palpably dropped (and I mean dropped: there was an actual sensation) into a trance state.
My limbs were heavy, my eyes were closed, and my mind very lucid; and I knew that I had somehow ended up in a trance. (Oh, and I also had a bit of a compulsion to take my clothes off?)

then the trance disappeared, and I sat back up again, going WTF?

So my questions are: What did I do? Does it happen to other people? and What does it mean?