Hi I have a 1991 Sl 500 I got it from my dad after my 2nd deployment to Afghanistan and I was very excited about it but I start having problems with it .
# when I drive it for 45 minutes and it gets hot the car won't accelerate any more and it don't move at all , but when u park it and it cools down its good to go , I took it to Mercedes dealership and they said it might be the ignition module but they weren't sure and they said just the part cost 3500$ just want to know what could be the problem

Yes, I agree with the Mercedes' dealer. It definitely sounds like a bad Ignition Control Module (ICM) and they are more than expensive on Mercedes. Try removing the old ICM and coating the back of it with silicone heat transfer compound (Artic Silver 5, Radio Shack). It likely fastens to a heat sink. If that doesn't work, you will have to replace it. In that case, consider going to a salvage yard--look for a guarantee.