Symptoms
Engine speed rising without the car accelerating, a bite point that has moved close to the top of the pedal, rattling at idle that stops when the pedal is pressed, or vibration through the pedal.
Likely cause
The friction disc wears through use, and heavily so in traffic. The dual-mass flywheel contains springs that damp torsional vibration; those springs and their damping grease wear on their own schedule.
How should it be checked?
Have the flywheel checked when the clutch is replaced. Fitting a new clutch to a worn flywheel puts the labour back in front of you.
How can you check it yourself?
In a high gear at low speed, accelerate firmly. If engine speed climbs faster than road speed the clutch is slipping. Listen at idle with the pedal up, then down.
The question to ask the shop
Has the clutch been replaced, and was the dual-mass flywheel replaced or reused at the same time?