Differentials:
Seizure - Ask for shaking, tongue biting, rolling of eyes, incontinence
Hypoglycemia - Sweating, fatigue, excessive hunger
Orthostatic hypotension - Ask for palpitations, positional syncope or hypotension associated with large meals. Medications can cause this. Counsel this patient properly by warning them and ask them to get up slowly, etc.
Vasovagal syncope: What were you doing when you lost consciousness?