That is interesting because when I read your initial post, the first thing that came to my mind also was a panic attack. You description was exactly what I feel when going through a panic attack.

It's also how I have felt right before I would pass out from not eating enough food.. when my blood pressure drops. Many causes for this kind of feeling along with some med also made me feel that way, but my first through was panic attack even when I am not really panicked about anything.

Hope you find an answer.....but body doesn't like to give up it's secrets easily
Debbie