depends on who's driving it, and how they drive, some have gone at 30k, some are still going at 90k
may not be the clutch,
sometimes the clutch master cylinder plays up, but this generally leads to the pedal sticking to the floor and requires pumping to get it to come back.
does it do it all the time or just when your first start it, and when its cold, may just need time to warm up. 1st gear is often juddery if your not used to the gear box.