I think it might be dissociation too. A psychiatrist once suspected that I was experiencing them while I was going through a really difficult time in my life. He explained that they occur when the body experiences "stress overload" and can't find any other way to cope. To be honest, they I didn't find them particularly unpleasant and just kind of lived with intermittent episodes for a while.
In addition, I used to experience dissociation as a kid whenever I went into large gyms. I'm definitely not agoraphobic, so I think it may have just been a sensory overload of some other kind.
Good luck!