I know how frustrating a stalling problem can be from my experience. People will finger you and say "look even mercedes can brake" or something like that. It is also unsafe to be stuck in the center lane of a highway or at the traffic light and wait for a tow car.
My car used to suddenly stall and be hard to restart too. I used to wait for 30 minutes to be able to restart it. First time when this problem happened it turned out to be a bad connector leg at fuel pump relay. I resoldiered it to the relay's inner board at no cost to me and everything was fine for 6 months and then the problem reoccured.
The car again would suddenly stall or have a very low idle for some time and then suddenly would be running fine. This time problem turned out to be a fuel pressure regulator. I bought one from the junk yard for $30 and that solved the problem. Then the car ran fine for 3 months.
You would be surprised to hear that a low idle problem revisited me a month ago. I then added a bottle of injector cleaner and got a smooth idle. Right now my car is running smooth and has no idle or stalling problems(nock on wood).
What I am trying to say here is that the answer to your problem might be anything. If the idle computer will get any bad signal from the sensor such as air mass meter then it will switch to limp home mode or might even shut down the car. If you can get some free advise from local mechanics about this problem that might be helpful. Good luck.
1989 230E, 8v, 166.000 km, updated to 94/95 trunk & hood
2002 Daewoo Nexia 50.000 km
1987 VW Jetta GLE 16V, Recaro seats
1982 Volvo 240 DL (lovely car!)
and few more american cars.