How to make my players hands shake in unity?

Question

I saw this video and saw the hand shaking effect that this game had, it made the animations and movement feel amazing. I would like to implement this in my game but I have no idea how I would go about that. The idea is that the hands shake slightly when the player is idle and then multiply when the player is moving or playing some animation. Any idea how I could do this?

Here is how the arms and gun are setup, I have no idea where to even start because I have never seen a game do this before and I could't find any documentation on this.