I have a 1992 300e with 82,000 miles which has a cold starting problem. The service records indicate that the car was only driven a few thousand miles over the last couple of years. I have had the car since July, 1999 and I don't know if the previous owner had these problems.
Fuel will occasionally foul out the spark plugs, making it impossible to start until the car is again allowed to sit to let the plugs dry off. After running several cans of injector cleaner through the engine, my mechanic thinks it is an intermittent lack of spark condition. He tells me that he can not get any computer codes to come up to tell him what is wrong. He first adjusted the flywheel sensor, then replaced a number of ignition related items like the overvoltage regulator, rotor, coil, coil wire, etc. He then replaced the flywheel sensor. He continues to think it is an intermittent lack of fire/ignition problem. Even if the car starts right up the first try, it will idle roughly for a few seconds before smoothing out and then it runs fine.
When the problem first began, the engine would begin to sputter while it was being driven, and it would shut off in the middle of traffic. It would usually restart, but once it began sputtering like this, it would continue to shut off and run rough at low speed. "Blowing the soot out" didn't seem to help. I haven't had this part of the problem lately, but I can't seem to shake the unpredictable hard start.
I have read some other posts from 190e owners with what sounds like a similar problem.