I had a spring go bad on the clutch pedal linkage & had this problem. Lucky me, it broke while I was driving (but not while using the clutch). I heard it break, so when I got home (having figured out right then that the clutch was still working - phew!) I did a bit of hunting & found where it had been & replaced it. I'm driving a 1987 F250 diesel with "heavy-duty everything" so I figure if it's your spring, it's in some other place than mine.. but you might take a look.
NOW - I have a question about clutches. I was sick last fall when my clutch went out, so I hired the job done at a local used-vehicle dealership that has a reputation for doing reliable work. Which is more than the local dealers can claim, sad to say. Regardless - I had replaced the slave cylinder maybe 2 months before the clutch went & had still got some air in it. When they replaced the clutch pack, they bench bled the slave cylinder, they said. Two months later when we had a run of -20F to -40F for a week, something went haywire in the clutch system again, because it went back to not wanting to take reverse unless I shut off the engine & then shifted. This is really rugged when parallel parking on a busy street, so I didn't like this.. Experimenting with various ways to get around this problem, I found that if I depress the clutch pedal to the floor 2-3 times, the truck will then shift into reverse, although sometimes the gears are still moving slowly, as I can hear it when I ease the shifter into the reverse position. Anyone have any ideas as to what I'm up against here? This has me & every local transmission fixer stumped. The dealers just said 'bring it in & let us try to figure it out' (at $70/hour. NOT likely.) I find no leaks.. No binds..