A two+ hour drive would really take it out of me. I would often have to stop and have a 10 minute nap.
I’ve found meds have really helped, I still feel tired, but I don’t have to sleep afterwards or take naps.
Same with riding motorbike, but double. I think it’s the intense concentration for long periods of time.
Even with meds. Not so much anymore, but when I was commuting to college. And not just when driving. I would get really drowsy seemingly randomly sometimes to the point of having little split-second visual hallucinations (extremely rare though).
Come to think of it, I was also taking Zyrtec (OTC allergy medicine) at the time, and I think drowsiness was one of the side effects. That might’ve been my issue.