Let me share my experience with you. This happen to me back in May 2003, just like the problem you have right now. My 88 300E died on a stop sign also. Some Mercedes shop will tow your car for free. I took my car into a Mercedes shop to save me money. Why did I say say save me money is because trouble shooting is better than guessing. Anyway the problem is the voltage regulator on my alternator. It drainned out my battery so it won't even crank my engine.