I remember reading in the Old Testament that it was sinful to shave off your pubic hair. Just like getting tattoos and piercings. Is shaving pubic hair a sin?
I believe you are referring to: "You shall not shave around the sides of your head, nor shall you disfigure the edges of your beard. You shall not make any cuttings in your flesh for the dead, nor tattoo any marks on you: I am the LORD" (Leviticus 19:27-28). It is referring to the practice of shaving idolatrous signs into the hair or beard, much like some shaving gang signs on their heads.
There were times when the Israelites were required to shave their entire bodies, which would include the pubic hair, such as when a man has been cleansed from leprosy. "He who is to be cleansed shall wash his clothes, shave off all his hair, and wash himself in water, that he may be clean. After that he shall come into the camp, and shall stay outside his tent seven days" (Leviticus 14:8).
In general, shaving the pubic hairs is not advisable because the area is moist and can be a breeding ground for bacteria and fungus. Shaving creates tiny nicks in the skin that can give bacteria and fungus a lodging place to grow.