What Causes Sudden Feel Of Light Headed And Nausea?

Tonight I suddenly became light headed and felt nauseous. After a few minutes I began to sweat profusely and felt very sick. This lasted for about a few minutes and has happened before. I wasn't doing anything strenuous as I was driving at the time and had not had much physical activity today. I'm 28 years old, 6'2'', 185 lbs. and I do not have a medical history and am fairly healthy. What could be some reasons for this?