I was in the store and i all of a sudden got really dizzy. what could be wrong?

Many things!: You need to see your dr! so she or he can get a full history, run some tests, check your blood pressure and heart rate, listen to your heart, do further exams, possibly an ekg or imaging of your head depending on your age and the events, what you ate and drank, etc. Prior to the episode. You could be anemic, or you may have even had a mini stroke. It could be "nothing", or a serious warning.

Common cause: Could be many things. But one of the most common causes is benign positional vertigo which usually resolves in a day or so. However sometimes it may require medications and certain exercises. Please talk to your doctor about it.