Shifting Feeling

I've noticed it happening a couple of times whenever I have a strong emtional response or feel very "Still" while meditating.

It feels like there is a copy (Or double) of myself and I am "Shifting" between the two versions of myself. These episodes last as long as the emtional state does, whether empty feeling or under some external emtional stress.

What causes these? What are they?

I felt like this a couple of times and when a friend confornted me over the "weird expression I was wearing on my face" I explained and she said that has never happened to her, so suggested I go back and write here about it.

When I asked about the look on my face she said that I looked very "Blank, no expression or emotion, - almost dead looking."

That freaked me out a bit. Anyway, I was sitting in the middle of class and this heavy but relaxed feeling began to creep over my shoulders and before I knew what hit me I had that "Shifting" feeling that lasted for a good five minutes and had almost no feeling within myself, - this time seemed stronger then the other experiences.

I googled it but it only came up with something called "Vertigo syndrome", and I am pretty certain that this is something different. I tried meditating over it a couple of months back but it just ends up with falling to sleep. (Not a very productive meditation then!)

So after it happening again this morning I've become extremely curious to what causing it and why it's happening. Does it have a purpose? Has anybody else experienced it or something similar?

Thanks!