I finally understand why Mario is shaking so weirdly in cold levels of Super Mario Odyssey.

First of all, the cold temperature leads to a cooler temperature in the body of Mario. As a response to that, the thermostat in his hypothalamus activates warming mechanisms such as repeated contraction of skeletal muscles that produce heat due to the friction they generate. That increases his body temperature as a response to the cool temperature.

It's amazing how Nintendo thinks of every detail.