This is a great question to be asking. Luckily, I have some information to tell you out so you can understand why people feel shy.
So when a person feels shy, their brain is interpreting a certain situation as a threat so say a person was talking up on a stage in front of others, their brain interprets talking no in front of a whole group of people as a threat. Usually people who are shy try to avoid any situations they can in front of a huge crowd or try to avoid eye contact. Also around 22% of people that are shy isn’t because their parents were.
I hope this helped you understand a little bit more.
People can be shy due to their life experiences. For example, a person who was once into rollercoasters, might have gotten into an accident in one. So that person would definitely be nervous to try it again.
There is also a fear factor involved.
When you are trying something new for the first time, your brain will immediately try to stay away from it. Its Kind of like an alarm in your head going DANGER DANGER! I DON'T KNOW WHAT THAT IS!
This is the same case with meeting new people. If a person meets a new person, most people won't talk much to them. But after talking to them and getting to know who they are, your brain feels less "scared" and you are not shy anymore.