See also:

Setting the interior/exterior lighting delayed switch-off time
Interior lighting: you can set whether and for how long you wish the interior lighting to remain on in the dark after you have removed the SmartKey from the ignition lock. Exterior light: you c ...

Mercedes-Benz M-Class Owners Manual
...

Vehicle remote opening
If you have unintentionally locked your vehicle (e.g. the SmartKey is still in the vehicle) and a replacement SmartKey is not available, the vehicle can be opened by a Mercedes-Benz Customer A ...