This is a common
problem with VW group DSG vehicles with the old style gearstick style gear selector.
The
problem is caused the the failure or grease and dirt contamination of a small microswitch that is located under the centre console at the front (dashboard side of the auto stick). The gear selector physically pushes and depresses the micro switch to indicate the "P" park position. When the switch fails the car cannot detect that the gearbox is in the parked position.
There are two solution. Firstly the "Italian Tuneup" method which involves slamming the gear selector in the "P" park position 20 or 30 times to clean up the connector surfaces in the microswitch. Secondly you can replace the microswitch by removing the top and side of the centre console and replace it with either the grey or white version of the switch. You will need the switch part number for that !
The good news is that the fix is cheap and is done from the driver's seat. No auto gearbox work is necessary. Look it up on You Tube.