Strange noise from near B-pillar

Hi all.

I picked up a new Superb 1.5Tsi e-tec MHEV SE Technology last week.
3 or 4 times since then, I've heard like a motor, whirring noise. It sounds like it's coming from the driver's B-pillar area. It lasts for about 2-4 seconds then stops. I can't be 100% sure of any pattern yet but when it's happened, it seems to be just after you pull away.

Google AI says it might be the seat belt mechanism setting up and taking up any slack, although I can't say I felt any movement on the belt.

Anyone have any ideas? Hopefully I'm worrying about nothing 😁