All the four doors lock automatically at random while driving on 1999 Volkswagen Passat

Once the doors get automatocally locked they can be opened with the lock / unlock switch on the driver side door

Asked by for the 1999 Volkswagen Passat
1 answer
sounds like you have automatic door locks which lock automatically when the car is in drive and the vehicle is travling at a specific speed which is usually 10MPH. Check your owners manual if you want to deactive this option.