I have a '91 300sl, it has recently developed a problem where it intermittently runs rough. after a short drive to the local grocery store we came out and it wouldn't run at all. It would start then run very rough (like it was on 4 cylinders). We walked home, went back a few hours later and it ran just fine. Someone please help as we just bought this car and love it dearly but the horror stories about the cost of repairs are starting to seep in. I am mechanically inclined and feel that I can do many of the repairs myself, except I have no idea where to begin on this one.
Thank you Michael

Could be sticky injectors. They leak after you shut off the engine for a while creating a too rich mixture. After a couple of hours the gas evaporates. Try a can a techron injection cleaner. Do it twice. Was it a wet day? That could be ignition.