Transmission problems

[Markymark101]

Hey people,
I'm a first time poster and it probably won't be the last post either. I have few questions if anyone is willing to answer them for me. I just bought a 98 SL500 and I'm having problems with the transmission. I was driving my car the other day and noticed it down shifted by itself. When I stopped at light and started again it would not shift out of first gear. I turned the vehicle off and restarted and it was fine until today it did almost the same thing but instead of not shifting it would shift very late and no lights came on. I've been a GM technician for 16 years and could tell you anything you want to know about GM car but when it come to the MB I'm a little lost. Does anyone know of a common problem with them?
I have one more quick question about coil spring shims. How do you know what size shim you have. I noticed in the front there were 3 notches on the shim and 2 on the rear. Does that mean anything?
Any help would be greatly appreciated. Thanks Mark