A lot of people experience back pain AFTER (not during) a stint of driving. Usually this has something to do with the way they are getting out of the car. When you turn and put your left leg on the ground and push off with your right leg to get out, there is a tremendous amount of torque and compressive stress at the knee, hip and sacrum on the right side.
To avoid this problem, try this…when getting out of a car, imagine that you are wearing a very short and tight mini-skirt (come on guys, it’s just pretend!). Swivel both feet out of the car before you get out of the seat. It is a lot easier on your back.