I also have this reflex.

I gently squeeze my mind (or something like that?) and get an immediate sensation of falling in my abdomen. Whoosh! I have never tried it for going OBE but it certainly is bizarre and interesting. I don't know where it came from or how I got it. As for what it is, no one really seems to know, but I think it is basically just chakra activation, perhaps the solar plexus.

I had a psychic give me a reading and she felt it too, so maybe it really is important...