Somewhat normal, it all depends on the condition of the brake calipers, master cylinder, and the amount of idle-torque the engine/trans is putting on the wheels, which can vary depending on engine idle speed and Bowden cable adjustment. Does it stop the wheels if you press the brake pedal harder? Ideally it should stop the wheels with medium pressure on the brake pedal. 300E usually idle pretty low, so it could be Bowden cable adjustment causing more transmission engagement at idle than there should be... Does the car have strong creeping movement/pressure when idling and in reverse or drive?

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)