The character is in a location where the temperature is about 0 degrees F.
Brrrr!! It's cold!
When the body temperature drops below 98.6 degrees F the body responds to this stimuli
Shake muscles SHAKE!
Your body will start to shiver in order to generate heat. Organs and muscles shake
When we're cold, the muscles around the hair follicles contract to prevent heat loss. These are goosebumps.
what are these bumps on my skin?
When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat.
This is your body maintaining homeostasis when the body temperature drops below 98.6 degrees F.
your body will continue this process until your core temperature goes back to normal and when you go somewhere warm.