Our body needs to maintain a core temperature of 98.6 degree Fahrenheit. It is our brain which monitors the body temperature very closely in order to prevent hypothermia and other such consequences due to cold.
Why do we Shiver?
Shivers are reflexes which your body shows to keep you safe and healthy and to signal you to keep yourself warm. Reflexes are controlled by your nervous system which in turn is controlled by your brain. When the brain sends a signal these nerves carry the information to each and every part of the body and the bones start to shiver. Your muscles start to contract and expand in a speedy manner. Your jaw muscles also might shiver which makes your teeth chatter.
What do you do?
You try to make yourself warm by either wrapping a warm blanket or having warm milk or even running or walking fast to get that warmth in your body.