I get dizzy often as well, combined low blood pressure and blood sugar. Sometimes I get super hyper first, but I always go from light headed, to no vision, no hearing, body is numb. Kind of like having a really heavy, dark blanket slowly coming over you...and by then I'm down and trying to recover, so I start coming out of it. Then I get sick, strong stomach though, so I rarely puke. Never been completely out, though, because it's a slow enough onset that I can sit down and take a moment to recover. I've had it happen when I've been sitting for a long period of time then get up, in the (very hot) shower, bath, at work when I was waitressing...so on so forth.
But anyway, I'd get it checked out just in case. If not ER, then make an appointment with your DR to get their opinion on it, whether it's a MRI, xRay, or whatever.