Battery problems of the 2001 Mercedes Benz 240

I have a 2001 c-240 Mercedes Benz, the left tail light keep blowing and I get a message that I'm using the substitute light, I took it the repair shop (Mercedes Benz) and they changed the bulb, now the problem is happening again in less than a year. There is a shortest somewhere and it also causes the car not to start only after a day of sitting, I have to jump it to get it to start. I called roadside service the checked the battery and said something is draining the battery, but when I take it in the repair shop can't find anything. A couple nights ago the alarm and all the outside and inside light came on for no reason. Please help. . . Did I buy a lemon? I love my car but want it to start when it's cold outside, has there been a problem like this reported on other c240. The battery has a good charge, so says the mechanic, but he doesn't know what could be draining it.

Vehicle will shut down completely with no warning. While at dealership, mechanic replaced battery, fuel injectors, and fuel related components , and some other electrical parts. Vehicle continued to shut down without warning. Mechanic could not locate cause of failure. Currently vehicle was surging. Please describe details.