sudden onset light headedness, nausea, with brief hot flashes. Usually lasts 1-3 hours, then dissipates. Happens at random times, irregardless of activity, diet, emotional state, or stress level (Which is usually low, but can occasionally spike, then immediately drop low again). Moderate caffeine use Moderate chewing tobacco use fair amount of junk food in diet bmi of 24.5 blood pressure normal to low range physically active in employment (50 to 70 hours per week) Maybe too much Pepsi and not enough water on hot days?