So... had a strange thing happen while at work today. When I went to take off from where I had had lunch, my ignition key did not work the first couple of times after the customary glow-plug warm up indicator sequence. I thought this a little strange since it has always just worked fine with the exception of once when a glow plug gave out. On the third try it finally worked, so I thought to myself, "perhaps the ignition switch is starting to act up a little bit?, I should watch that"...

When I got back to work only a mile or so away and switched off... I heard this weird low rumble/vibration noise. At first I thought perhaps my radiator fluid was boiling like crazy... but it's not that hot here and i hadn't driven for that long at all... I popped the hood and it was such a strange noise... almost as if the engine was still running, but it wasn't?... I think I saw that one of the glow plug posts or wires was starting to glow red-hot... I couldn't figure all this out and had to get back in to work, so I quicklly disconnected the battery... sound stopped.

I was hoping that after cooling down for a while the problem would go away, but after work, every time I tried reconnecting the battery I would get the same sound. I narrowed it down such that I'm almost certain that it's my starter motor spinning very fast and making a disturbing racket...

I had to leave the car at work... and I was hoping that some awesome benz-nerd here in this great forum could help me out with this perplexing problem?

What do you all think of this one? Should I try hammering on the starter from below perhaps... checking a relay... what could be causing this circuit to be still engaged with the key turned to off or not even in the ignition?

Thanks all... hopefully I can go rescue my car tonight and not leave it out in the sketch area where my company is...