I suffered from panic attacks for years. I think they started in my early twenties. I can't really remember the catalyst for them. It was different each time but I remember the last really big one I had was on top of a ferris (sp?) wheel back home. We went on with some friends, I wanted to be there, it was a lovely day. It stopped at the top, we were chatting away and all of a sudden it jerked and full blown panic attack. I started hyperventilating (for lack of a better term), my peripheral vision cut out and I remember a voice from somewhere (DH) talking to me to calm me down. It was over by the time the wheel finished it's trip and we got off.
Incidentally, I haven't had one in over four years, since I've been on seizure medication. I don't miss them and I barely remember them.