I shake when I fall off

This happens because the body's sympathetic stress system kicks in, also known as the stress response. It does so because the brain has registered some form of danger. The muscle shaking comes as the brain readies the body to act if it needs to. Many thousands of years ago this response let us act fast and run or fight if we had to. Plenty of people get this surge when they come off, when they are frightened, when something unexpected happens and so on. It is completely normal ❣️