They have all kinds of heat & massage units that plug into your lighter socket these days. As a starter, why not take a small cushion or roll a towel into a cylinder to place between your seat and the small of your back for lumbar support. I think they have some heating pads that you can nuke for a while to add heat without plugging in. Beyond that, make a rule for yourself that you wont drive more than ?.? hours without getting out to stretch for a few minutes.
Joe
