My 88 300ce (M103.093) began stalling about 3 weeks ago. Going down the street, say 35 mph. Just stop. Pull to side. Put in park. Restart immediately. Stalled the next day too. Then ran fine for a week. Then stalled on Sunday in traffic again. Drop into neutral still coasting & immediately restart. The next day it stalled twice and the next day 3 times and the last time it wouldn't immediately restart.

Towed it to a dealer. They diagnosed it as a bad fuel pump relay & replaced same. Got it back last Thursday and it has run fine ever since. From the service bill, they indicated they were able to replicate the stall and then diagnose the problem. I don't know if it's BS. but if it was an educated guess, they guessed right in my case. (Or so it seems so far.)

Do a search on M103 stalling and SSS (sudden stalling syndrome) The problem could be from a number of sources. There are a few current threads on this, with multiple suggestions.

My car had no other symptoms other than just stalling. It ran smooth. at idle and at all rpm's. (That is, right up until it quit )

Funny, that they listed the part as the "fuel pump relay" and when I searched this site here for price comparison, there was no part having the same name.

Good luck.