[BobaFloutist]

That will randomly and unpredictably try to take over tasks from your other limbs, hijacking your somatosensory system so you can't tell when it's doing so without actively looking at what you're doing.

[dylan604]

I think you just described my cat's tail

[robocat]

Alien Hand Syndrome: https://en.wikipedia.org/wiki/Alien_hand_syndrome