why doesn't the headlights turn on

Hello, That sounds just like the bulbs burned out on you. When these lights go, they tend to flicker sometimes, then they will only come on when they want to, then, finally, they go out. Having one fail after the other is not a big shock, but you will need to test that the ballast is getting power before spending 1-200 dollars on bulbs. If you would like info on testing the ballast (the part the bulb plugs in), let me know, otherwise, here is a list of certified facilities in your area: http://repairpal.com/mercedes-benz-within-10-miles-of-cambridge-massachusetts-02140