When you say it won't start I'm assuming that when you turn the key, the engine does not turn....you do not hear the starter or engine do anything. Also, the lights come on and are about as bright as normal.

If the car has an automatic transmisssion, this could be caused by the shifter switch. Basically, there is an electrical switch attached to your gear shifter that keeps you from starting the car when it is in gear (aside from Park or Neutral). This switch could be going bad or just coming loose. If you don't do any service work yourself, have your mechanic check this out for you. The part is about $50.

In the mean time, if the car fails to start you can try two things to get it started.

1)With your foot on the brake, move the shifter from Park to Drive and back again. Then try starting it. This could bring the switch back into contact.

2)If you are confident under the hood. Open the hood. With it in Park, turn the key to the on position. Use a long screwdriver to jump the terminals on the starter solenoid and it should start. This bypasses the ignition circuit. If this step does not make sense to you don't try it. Just have the switch checked out.

Good Luck,
MORMIT
1985 245DL 230,000mi "Inga"
2002 S40 2,500mi "Sigfreid"