I have nearly 100K miles and am starting to feel a slight vibration in the clutch pedal. The vibration seems to only happen when shifting from gear to gear and not from neutral to gear, generally when letting the pedal out. (engaging the clutch)

Let me clarrify, say driving along, shifting from 2 to 3 or 3 to 4 or 4 to 5, I feel a high frequency vibration. It can only be felt through the foot. However, if clutch in, shift to neutral, clutch out, wait until the revs come down (this may be seconds or longer if I am coasting down an off ramp or something), clutch in, shift, I don't feel it.

It's just a slight vibration, like a hum or something. A lot of my driving is highway (60-70%). I don't slip the clutch too much. I don't rev-and-dump. I do accelerate hard once the clutch is fully engaged. I always (90%+) coast / idle in neutral with the clutch pedal out. (clutch disengaged)

TIA for any insight.