I have a 2007 GL450 and when I turn the wheel a 1/4 turn to the left or make a left-hand turn, the driver-side headlamp (bi-xenon) turns off. Once I straighten the wheel it comes back on. By the way, I just had my Steering Angle Sensor replaced (if that has anything to do with it). This does not occur with the passenger-side headlamp. NOTE: as a standard function the "fog lamps" temporarily come on when turning left or right.

 

Sounds like this and other issues you have going on is due to bad or missing reset/calibration of the BAS/ESP system.