Strange rumbling from rear wheel/s intermittent

[Andrew Macrae]

This is a strange one to me so maybe someone here has or had same problem and can maybe enlighten me . A4 Quattro 2.0t b7 , usually after a bit of a drive ..I’d park up nip into a shop say then reverse or drive car forward and get a weird grinding or rumble from on of or both wheels , I’m saying wheels as seems obvious choice , goes away once speed is up and when traveling at normal speeds feel or hear no noise . Car has just 109k and not been bad used with FSH , any help folks would be appreciated. 

[Steve Q]

Wheel bearings is an option but I'm wondering if a brake caliper piston or handbrake is sticking. 

Id be getting it booked into a garage for a proper diagnosis.

Cheers

Steve