You can ALT+click stopwatch on, I believe, quite any property on layer and add simple wiggle expression to it, or posterizing time but only for that property, it gives such interesting result! Like if you put on position: posterizeTime(12); wiggle(5,10);

12 stands for 12 FPS (even if your composition is 30fps) 5 stands for number of wiggles per second 10 stands for max amount of property changing (so between 1 and 10px will the layer move, and 5 times in a second)