I have had this for a long time and have yet to find a reason as to why it happens. Nothing I've noticed in my over 34 years has provoked it, it's a sudden onset with no clue why. I as well have yet to find a way to get back to normal other than wait it out. The worst is when it happens while I am driving, I had it happen on a cross country with my wife and kids, I had to pull over because I was unable to concentrate on the road because of my mind racing. It only happens a few times a year, maybe 3 or 4 but it is a definite inconvenience. Maybe it's time to bring it up to the Dr. I thought for a long time I was probably just imagining it and was the only one. Glad to see I'm not.