Why do the hazard lights on my Mercedes keep turning themselves on whilst parked?

Not brake sensor but brake switch can cause that, its located behind the brake booster in the engine compartment, make when you apply brake your lights comes on, if they don't come on then you have a bad switch or a blown brake fuse and this will cause the gear lever locked in park

have you installed an aftermarket alarm system? if so it was a lousy job.

That is an indication that the alarm has been triggered. Does the beep work when you lock or unlock the car? If it does not sound when you do that, the lights are likely the alarm triggered. Check the hood switch, which is a common problem around this age...

The parking lights, dash lights, turn signals, and hazard flasher should be 4 different circuits.
So you would need to know exactly what that fuse protects, then look for the short to ground.

Do the hazard lights work ?

see the diagram and fix it.Test the fuse,lose connection, dirty, corrosion, oxide.continuity.
God bless you

check remote batteries for replacement. they may be dead as for the door locks and trunk. as for the fog light, parking brakes situation a short would make them not work. not stay on. the electrical would be fused for that. a short prevents electric from getting to the load or device. i would not think that fog lights would be linked to parking brakes. did you mean parking brake light? the fog lights should be on a switch by themselves or connected to main headlamps

What relay's ?
The instrument cluster controls the headlamp systems that include daytime running lamps (DRL). The system allows the headlamps to operate at a reduced intensity when all of the following conditions apply:
• The engine is running.
• The transaxle is not in the PARK position.
• The normal headlamps are not on.
The instrument cluster turns the DRL system on by grounding CKT 592, thereby energizing the DRL relay. This action allows a reduced voltage of 6 volts to flow across the headlamps. If the vehicle has the optional fog lamps, the fog lamp relay will also be energized. The park lamps will turn on and the fog lamps will operate normally. When the headlamp switch is turned to the ON position, the instrument cluster allows normal headlamp operation.
The instrument cluster also has an input from the park brake. If the park brake is in the ON position, the DRL will remain disabled until the park brake is placed in the OFF position. On vehicles with an automatic transaxle, the instrument cluster will disable the DRL until the transaxle has been taken out of the PARK position.

Headlamps Inoperative - High Beams
Step
Action
Value(s)
Yes
No
1
Did you perform the Daytime Running Lamps (DRL) System Check?
--
YES - Go to Step 2
NO - Go to Daytime Running Lights (DRL) System Check
2
Disconnect the turn/hazard headlamp switch connector C1.
Connect the fused jumper between terminal B of the turn/hazard headlamp switch assembly harness connector C1 and ground.
Do the high beam headlamps operate?
--
YES - Go to Step 3
NO - Go to Step 4
3
Replace the turn/hazard headlamp switch assembly.
YES - Did you complete the repair?
--
NO - Go to Daytime Running Lights (DRL) System Check
--
4
Repair the open in CKT 1200 between the turn/hazard headlamp switch assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
Go to Daytime Running Lights (DRL) System Check
--

My 2006 Uplander would not shut off the parking lights. I came here for a solution. I saw the answer here, actually the question, and I used the key fob to lock the vehicle. The lights went off. That was a temporary solve. Now, is this a "glitch" or a "feature"?

possible headlight relay under plastic screwed down cover behind fuses.