To me, it sounds like a panic attack. Try to meditate or prepare yourself before going in to a situation you know is likely to be stressful. Tell yourself exactly what you're going to be facing and that you can handle it. Look at the time and tell yourself when you'll be leaving. I find that I can handle stores or crowded places if I prepare myself ahead of time and know how long it's going to last. If I go over that time, it becomes hard to control. Start with just a small amount of time and build up. If you're in a situation where you're sitting down and the feeling starts hitting, close your eyes and breathe for a few seconds, focusing on your breathing.

Maybe it happens when you exercise because you're anticipating something happening again? Once again, prepare yourself before you start. Exercise for a very short amount of time (5-10 minutes) and increase it. Don't allow yourself to get totally stressed out or panic. When you feel it coming on, try to control it and if you can't, get out. Some things are just not worth getting all stressed out about. And, sometimes, trying to control it makes it worse because you panic about your panicking! Stay in the moment...don't let it build up like that.