This happened to me...but it was always related to meds. If you're not sleeping well then it could just be being over tired too (I've had THAT happen after working overnight shifts).

Be very careful Alt. I didn't drive for over a year because my RSD symptoms made it very dangerous for me to do so (dizziness, blurry vision, etc) and I didn't start driving again until I got those symptoms under control. I was VERY clear with my doctor how often these things were happening and it was something she put in every doctor's note for work...that it was unsafe for me to drive (even though all my other symptoms also prevented me from being able to work at the time).

Definitely get with your doctor to determine the cause of this and if it's happening often I would not get behind the wheel.