1990 Geo Prizm Braking

While driving the brakes seem to activate. It starts with a feeling that something is slowing the car and gets worse. It progresses quickly to the point that I can only move the car in low gear. I must pull off to the side immediately. After the car sits for an hour or so everything is OK. This does not happen all the time. I have recently driiven it 13 miles with no problem. I left it with a garage and he drove all over town and nothing happened. I have had the brakes inspected, some parts replaced, and the next day it happened again.
Is this a brake problem? What causes the stoppage to occur? Could it be the clutch?
Appreciate any information
Sincerely Ray McClean