Date registered: Dec 2005
Vehicle: 222.132 & 221.122 & 212.025 & 906.633
Mentioned: 3 Post(s)
Quoted: 32 Post(s)
If it cranks fine and lights are OK, it should not be an alternator issue. Or if there was one, it would not prevent the car starting.
This sounds more like a CPS sensor. From the W210 section you can find some good info (not sure about the W203, I don't follow that).
Of course it would be useful to have the real malfunction text, you might have more than one issue with the car.