Seat problems in R170 (back pain)

Hello all, I bought a SLK BJ. 2000 for Christmas, and now I have to find out that I can’t really drive it! After distances under 100 km I get back pain because it is too hard for me. My question is now, is there a way to dampen the seat at SLK (e.g. swing seat, or…) or other shock absorbers that make the car a little softer? Has one solved this problem in any way? If I can’t get the problem solved, I have to use the As car unfortunately sell again. I am grateful for any serious hint or tip. Greeting Robert