Static electricity (ESD) is generated when there is friction between the human body and clothing or surfaces. Clothes are easy to produce static electricity. Static electricity is also common in dry weather conditions such as during winter.
The more static electricity, the higher the probability of shock especially when you are in contact with a metallic surface such as your computer body.
You can try to remove static electricity before touching your computer:
A. Touch a metal object, such as a metal door;
B. Wash and dry your hands. Water helps to remove any static charge on your hands.