The buzzer relay. Is what your hearing. Make sure the door
switches drivers and passenger doors are ok open the door look inside the door jams. See if they plunge in and out easily/make sure there not broken. If there ok/ the warning buzzer/chime relay if fauly. The solenoid contact in the relay stick some times. Remember a relay is just another switch that can carry a higher load.
This should fix this complaint.
FACTORY MB TECH 14 YRS