When I stand up too fast, I usually get dizzy, sometimes to the point where I have to sit down. It's possible that I'm malnourished and I'm on a medicine that lowers my blood pressure so I'm not concerned about that. What I am concerned about now is that I've had some episodes where my muscles just started spazzing and I couldn't control them. The episodes usually were only involving my legs and occasionally my arms too, but I always had warning of a few seconds and could sit down. However, this morning I had another episode with very little warning and I didn't have time to fully sit down so ended up half sitting half falling down and the spasms were everywhere. I'm not sure 'cause I was alone at the time, but I may have passed out for a second or two at some point. What is this? I already know I have a heart condition, but that's not what's causing this. I'm just scared it's gonna happen at work or college.