My controller vibrates by itself

Hello,
My problem is that I got a PS3 controller from my parents. It was working, but this weekend it started shaking for no reason. When it's plugged in, it vibrates on its own and I can't use it; it gets stuck vibrating. Sometimes it stops, but after a while, it starts again and doesn't stop this time. I took it apart to see if there was a loose connection somewhere, but I don't know anything about controllers. Thank you for helping me :)