Use the motion sketch. On your timeline, set an in and out point for your vibration. Go to ‘Motion Sketch’ it’s under ‘Window’ on Mac, not sure about PC. Click ‘Start’ capture, grab your layer or comp and shake the mouse around for the duration of your in/out points, it should simulate a shaking. Tip: to get small, less obvious shaking, zoom in on your comp window, the more you zoom in, the less shakey it’ll be, almost like vibrating.
jv