Not sure your year w126
Typically when the doors are opened, the puddle lamps on each door should light, the dome light has 3 switch settings, off, on with doors open, on/map with doors open or closed. The rear dome, or reading lamps depending on spec, has a switch on the dash center console that is also typically a 3 way likr the front dome switch.

Door switches, burnt bulbs, or possibly frayed door/chassis wiring are places to investigate

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)