starter won't turn over in our 2006 mercedes slk

Check battery voltage and battery terminals. They must be clean and tight. All because the lights come on does not mean that the battery has enough voltage to crank the car.

Its what i call a dumb key,your dealer calls it a smart key,your key has a chip in it which must verify the code that is in the computer of your car to turn starter,lights and all will work.The chip in the key is possibly bad.You will need a dealer programmed key.But just maybe you have another one laying in the house .if your lucky : )

Did you figure it out ?