You should sit straight in the driver's seat in the way the pressure on the intervertebral discs is distributed more evenly (the spine should be leaned upon the seat back); don't move far from the pedals, you should correctly adjust the position of the headrest and, if necessary, put the contour pillow under the lower back. Buying a new car, you shoud be guided not only by its price, external or internal technical specifications, but also the seat and headrest comfort.
If you have enough of time and opportunity use it to visit the fitness center. Pilates exercises are good to prevent back pain. Pilates will improve your body posture, strengthen abs and back muscles. Swimming is considered as ideal sport for spinal. Try to hang on the bar as often as possible. In the summer, try to change your trips in a car on cycling.