When I'm in a car (driving or riding), sometimes my POTS symptoms flare up like crazy - my heart starts racing, I get chest pain, nauseous, and dizzy. It always happens on long trips (over an hour) but sometimes even on short trips after only twenty minutes or so in the car. If I pull over and stop the car for a while, things gradually calm down until I resume driving again. Does this happen to anyone else? Does anyone know why it happens or what I can do about it?