Have you tried pulling the pedal back with your toe? How do you get it rolling again, just waiting it out?

Like George said, if the MC piston isn't coming all the way back it's not gonna relase the line pressure back into the resivior and every time you push the pedal you'll increase the residual pressure in the lines till it locks up. This also allows the fluid to backflow as you get thermal expansion.

I've had that happen with 'Tater, the spring was too loose on the end of the return so it wouldn't release the line pressure, a new spring fixed that.

1956 GMC 370 dump " 'Tater "
1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI

I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P