Why does a human body shiver?
First of all I would like to tell that not only human body but also the animals who feel cold shiver.
In detail I would like to say that an animal's body does not shiver at all.
Instead the human body needs to stay at the normal body temperature which is said to be 37 degrees Celsius.
And the real cause is that when the cold air around us touches our skin cells the tiny censors beneath our skin cells send the message to the brain then your brain sends messages to nerves all over your body telling your muscles to tighten and loosen really fast which is what we call shivering.
It does this because when muscles move they generate heat.