Good Morning,
Great Info shared with you already.
Sleep apnea is a common sleep disorder where you stop breathing during the night, often hundreds of times and for as long as a minute or more. When you prevent breathing, oxygen levels in your blood fall and levels of carbon dioxide increase. This causes the heart to pump more strongly and occasionally to beat irregularly, or even to stop altogether for several seconds. Your chest and diaphragm muscles work harder and your blood pressure increases. Eventually, the brain senses that your body is in trouble and wakes you sufficiently for you to start breathing.
What you described, IMHO, could be orthostatic hypotension which was already mentioned or you might look into having his Blood Sugars checked for hypoglycemia. Another major cause of fainting is a slow heart rate.
He does need to see a physician as fainting is not normal, something is going on somewhere. You might tell him that going to the physician's on his own beats an ambulance ride if he passes out and you cannot wake him up :)
My hubby does not like to go either but I am not to proud to harp at him.
Keep posting and know we care.
Kitt