Why does my body shake while working out?

Your body shaking when you're working out is normal. It's because you are pushing your muscles out of their comfort zones (you aren't doing push-ups all day every day!) and so the energy required to perform the activity is surging through your muscles in overdrive, causing them to tremble a bit. That's not unhealthy, as it's strengthening the muscle!

In order to stop it, you just have to keep going. As you teach your muscle how to respond to the energy coming through it (by continuing to exercise and continuing to strengthen the muscle), it will stop shaking (usually; there are some exceptions I'll mention in a moment). You'll begin to notice that the shaking is reduced. But when you reach a new challenge (for example, doing pull-ups AND having weights on you), you'll feel the trembling again as your muscles start learning to strengthen again.

I did say there were some exceptions. Remember that whole human beings are pretty big compared to the size of the muscles in our arms. Unlike our finger muscles, which are fine-tuned for small movements, our arm muscles are made for larger motions. That means that if you try to do a pull-up or push-up slowly (in small, incremental movements), you will tremble. The stronger you get, the less you will tremble. Trembling is all caused by energy moving through your body and fueling the muscles doing the work.

if you have just started working out it will be because your muscles arent used to that kind of effort. dont worry it happens all the time. my dad is a personal trainer and he gets that question really often. soon enough you'll stop shaking dont worry