My fiance blacked out while driving and has been having dizzy spells. he's not on meds, doesn't drink. he wasn't standing up or doing anything. what c?

He needs a workup: He must see an MD to work him up from a cardiac and neurologic standpoint. This could be very dangerous even life threatening.

Blacked out: This can't be diagnosed with the information that is available. A history, physical examination & other studies may be needed to determine cause/causes. Once accurately assessed a treatment plan can be developed. He needs to stop driving now and get prompt medical evaluation.