1999 Mercedes-Benz C230 Question: my C230 won't start sometimes

So when you push the START button nothing happens?
On these models quite often the BAS (Brake Controller) module has a bad connection due to corrosion - caused by moisture. The BAS won't see that the brake pedal is applied therefor won't allow cranking.
I'd ask a MB specialty shop for a diagnostic, with SDS (OE diag. computer) they can see what the BAS "sees".
Of course there could be many other issues, like Crank Position Sensor, that's why the diagnostic is necessary.

Zee

I have a 2003 Kia Spectra. The same thing happened to me shortly after I bought the car in 2005. It wouldn't start, or crank, but after leaving it for a little while it would start up fine. I replaced the battery and had three different mechanics look at it. Finally, the dealership mechanic figured out that it is an electrical problem. He said it was something he couldn't fix, however, he said if I put my car into neutral it will start right up. He was exactly right. It happens every 6 months or so, and I just put it in neutral and the car starts. The mechanic also suggested, that if putting it in neutral doesn't work, If move around the fuse boxes, it should do the trick.

Give those a try, and let me know if that helps.