A sleep test might be in order. Ask your doctor.
I used to drive a lot as a musician. The coffee/cola jolt stopped working after a few years -I would "crash". What worked better for me is staying hydrated - lots of water - and food with few carbs. Protein or nuts as a snack.
Hope you get an answer soon!
"When I think of Mick Jagger still singing that he can't get any satisfaction in over forty years of being in the Rolling Stones, I have to conclude that he's either lying or not all that bright." -- Henry Rollins