It sounds like a classic panic attack. I would suggest you google this:
Symptoms panic attack
If what you read does not describe anything you experience, then see a general practitioner for an evaluation.
Can't really say what is causing it, could be important or could be nothing but you should go and see a doctor and get checked out. Just try to describe as much as you can about what happens, what you feel and when it happens. Best of luck sorting it out.