Using the rain sensor's memory function
The rain sensor automatically starts the windscreen wipers based on how much water it detects on the windscreen.
Activating/deactivating the memory function
The memory function for the rain sensor can be activated in such a way that the rain sensor button does not need to be depressed each time the car is started:
Tap on 
in the centre display.
in the centre display.Then tap on More.
Select Mirrors and wipers and activate/deactivate the rain sensor's memory function