twiddle
To fidget by turning or playing with something in your hands.
To twiddle means to fidget with something in a restless, often aimless way, turning or twisting it in your fingers. When you're waiting for something to happen and you start spinning a pencil between your fingers or playing with the strings on your hoodie, you're twiddling. Someone might twiddle their hair during a boring lecture or twiddle a pen cap while thinking through a difficult problem.
The word captures that absent-minded fidgeting people do when they're nervous, bored, or just need something to occupy their hands. A musician might twiddle the knobs on an amplifier to adjust the sound. You might twiddle your thumbs when waiting for your turn in a game, literally rotating your thumbs around each other, though this phrase has come to mean sitting around doing nothing useful.
Twiddling isn't necessarily bad. Sometimes fidgeting helps people think or stay calm. But if you're constantly twiddling with someone else's belongings or can't keep your hands still during class, it might distract others. The word has a light, somewhat silly sound that matches the small, repetitive movements it describes.