When I decide to take a ride and the temps are in the low 50s or down in the 40s the brakes are pretty much locking up my bike. Why is that? I will slowly rock the bike and they come loose enough to put it in gear and slowly go around the block. By the time I get back around the block they are free again and will remain free until the bike completely cools to ambient temps again.
Never happens in warm weather and have never had an issue with brakes on the bike.
Change fluids yearly.
I'd first try taking the brake pads out and cleaning and lubing the retaining pins. If they're dirty, and especially if they have old grease on them, they may not be moving like they should.