For the past year or two, about a couple of times a month, my eyelids get so heavy
while driving that fighting it takes all my energy and focus. This usually happens on drives longer than 30 minutes, but has happened with shorter drives. I don't *think* I'm exhausted, but this really only happens in the car, and can happen in the passenger seat as well, where I'm known to nap. Once I'm out of the car, I magically become aware and awake like I was before the drive.