calipers sticking on. give a strip down and clean and grease. check pads for uneven wear. its probably just sticking on one side . find out first

Possible pads/shoes rusting to the discs/drums, i assume this is either parking the car after driving on wet roads (worse with salt down) or after washing the car?

Or do the brakes need a proper service anyway, and one or other pistons/sliders/adjusters is seizing, i'm assuming here rear discs where the parking brake also applies the rear pads via an internal caliper self adjuster, horrid design that inevitably cause issues at some point on lots of makes.