This is a strange one that lots of older BME's suffer, There are lots of reasons but the most common is the splines from the gearbox rusting up along with the clutch release bearing, clutch plates last a long time before they wear out. Try pumping the clutch pedal a dozen or so times before going out, it may make all the difference and may cure the problem. The actual clutch housing condensates causing the rust to form. Lastly the flywheel can distort on higher milage cars but rarely, a garage inspection is costly so hopefully pumping the pedal will work.