I am experiencing intermittent brake pedal vibration. The brakes seem to function normally otherwise. The vibration can be felt in various operations. Idling while shifting. Low speed braking. High speed braking. Normal braking. It is a very high frequency, low amplitude vibration - almost like getting a mild electric shock. Higher frequency and lower amplitude than the common/normal ABS vibrations. The timings of the pedal vibration is the same as when I would previously hear (what I think is the) power/servo brake pressurizing the system. I don't fully know how the system works, but I believe there is a servo that assists/pressurizes the system in anticipation of a braking operation (ie it can initiate during initial light braking). The original sound seemed normal/faint. This new vibration seems abnormal, enough to startle a driver not familiar with the behavior. No warning lights, ABS system and braking operations seem normal.

If there's no problem in the brake system, maybe the vibration is in the engine bay and making its way to the brake pedal.