I have a 2010 R 350 Blue Tec.
Recently the car has decided to either turn on, or not turn on, depending on its mood. When I turn the key, the system is either 100% non responsive or the opposite. I think that there might be a problem with the security system. Any suggestions?

 

it could be the ignition switch, very common issue on GL,ML, R, sometimes when turning the key it will start, other times turning the key does nothing, usually on the second try it will start. If you take it to a benz dealer, they can run it for fault codes. it will say something like "circuit 50" not detected, or some other EIS fault code. could also be a bad key/remote