I'm sorry, but this sounds too weird. Does he have inner ear issues, like vertigo or something? Otherwise, it sounds like his overall level of conditioning is just so bad he needs to start somewhere - like fast walking.
He should also be drinking a lot of water every day, clean up his diet, try to work out at least an hour after eating, hydrate during the workout, and breathe evenly throughout. If he's been to doctors and specialists about it, he probably doesn't have an actual physiological problem - at least not one you're going to discover here.
Make sure he's not exercising on low blood sugar, and have him take a dramamine or motion sickness pill or two the night before working out. If it's motion sickness, or he's got balance issues, this should help. If it doesn't, he's probably got a bad case of: out-of-shape or *****-itis.
