Been a common issue on a lot of the models since mk4 onwards, not just Golfs, across entire VW, Skoda, Seat ranges... no one seems to be able to pinpoint the issue (which means marques can poo poo it as a non fault a lot easier)
Common thoughts are it's either a fault on the CCM, water ingress, dried out solder joint.... any other number of options or it's a thermal regulation type response. Get's too hot in the car, the windows crack open a bit to stop a pressure build up. I don't personally buy the second reason.
Ultimately no body knows for sure, but I HIGHLY doubt that it is the global opening feature being triggered all the time.