* There are several posts about people taking their Benz to Autozone for a (free?) fault code scan. I've never tried this myself (since I own the test equipment) but it might be worth a try. Since your car only starts and runs until it's at operating temp, getting to an AZ might be a problem. If you've got one closeby, call ahead to make sure your AZ branch can handle the scan (and since a scan is done with the ignition on and the engine off, you may need to plan on a wait while the engine cools down).
* You could probably install a resistor across the coolant temp sensor plug and trick the control unit into thinking that the engine is at a constant 20degC. There used to be a little test harness for the M103 engine that did just that. Incidentally, I replace coolant temp sensors just for good preventive maintenance. They're cheap, easy to install, and get rid of an assortment of irritating, mysterious foibles.
* There are also posts on this forum explaining how to make a rudimentary scan tool. That's likely more of a hassle than it seems, complete with "surprises" and complications, but it's a possibility. Sorry I don't have a reference for you, but a DIY search (homemade scan tool) or a PM to a moderator should get you some references.
* You'll probably want to do the scan in two parts. Read/record the fault codes. Reset (delete) the fault codes. Use the car thru several drive cycles. Be sure to try the unsuccessful hot restart in your driveway. Then scan for fault codes again. Some of the old codes might be gone and there might be new ones.
* You're probably aware that there are fault codes that give you a failed component, and then there are many more fault codes that just tell you a condition (like a cylinder misfire) which you probably already know.

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ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536