"What's your occupation?"

That is a good question. In the bad old days (before retirement) I had a job that I really enjoyed, I was more "up" at the end of my shift than the start. Even after a hard graveyard shift I never had a bit of trouble with the half hour drive I had...

There are some medical ailments that cause sleepiness, here is a like to only one...http://www.sleepydust.net/chronic-fatigue-syndrome-causes.html

But I think that I would look at my job itself...