system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why we get nervous and start shaking?

I'm like that.
gpt
From yahoo: Yeah, it's a side effect of the adrenaline and collagen that your body releases during stressful times. Mother Nature didn't intend for us to be put in the kind of stressful social situations that we find ourselves in sometimes, but our body doesn't know the difference. 

When you get stressed out, your body illicits the same response that it would if you were being attacked by a grizzly bear. Your body uses adrenaline and collagen to prepare your body for the "fight or flight" response. Basically, it is a way for your body to maximize the use of your muscles in the shortest possible time period. 

When you don't use that energy, your body might start to use it automatically, resulting in uncontrolled shaking.

**TLDR: Adrenalin rush**