clutch problem on the E21

[E21_Ross]

right, my clutch seems to be playing up a little bit and i'm not entirely sure what it is. basically, when driving along, it selects gears fine....but say if i'm stuck at the lights with the clutch down, it begins to want to move off and the biting point is very different, anbd the pedal does not spring back like normal. but once i've selected 2nd...then 3rd and so on, it's fine. its also bad if i go into reverse, reverse for a small bit, leave the clutch down, go into 1st and go to move off, with the clutch down i move out of reverse, and sometimes it won't select 1st, as if i'm above the biting point so i lower the pedal more and it works, but with a lower than usual biting point and sticky/non-springy pedal return. however, if i put it back into neutral and pump the pedal a few times, the normal feel returns and it sets off in 1st like normal.

the clutch is new-ish and has only about 5k miles on it so it's not the clutch itself. a while ago (about 10-11months i guess) the car suddenly wouldn't select gear even if i mashed the pedal to the floor so the following work was done:

"renew clutch slave cylinder repair and top up master cylinder and bleed."

so surely it can't be the slave cylinder as that is renewed about 8k miles ago...could it be the master cylinder going??

thanks for any help guys and cheers for reading.