The "Random" tool is able to randomize all kind of things (property values, keyframe times, layer times...)
First, open the "Random" panel by clicking on the "Random" button.
You can choose:
- Current values: randomizes the selected properties, adding a keyframe at the current time if the property is animated.
- Layers: randomizes the layers times, or position in the layer stack.
- Keyframes: randomizes the selected keyframes values or times.
If you "Separate dimensions", each axis will be randomized independantly, but with "collapse dimensions", the same random value will be used for all axis (which is useful for scale).
You can either use the random value as an absolute value, or an offset from the current value.