Feel free to move this to drivetrain forum.

I was sitting in the car today for about 25 minutes with the engine running. When I drove of the clutch felt heavy and the clutch started slipping on hard acceleration. The clutch feels fine when the car is cold or on long motorway trips but feels heavy when stuck in traffic around town.
Is this just the first signs the clutch is on the way out or could it be some other problem as it's fine when it's cold.

Cheers

Jeremy