I have felt a weird and quick numbness on one whole side of my body. what could this be?

Numbness: It is not possible to diagnose or suggest adequate therapy without adequate history and physical examination. However, your symptoms may alert your physician of either brain or spinal cord problem. At your age, a myelin disorder is a possibility. I suggest you discuss your symptoms with your physician to asses the need of further testing with an MRI of brain or spinal cord. Hope you feel better.