Shyness is deep rooted. It can be fear for some. A shy animal is afraid of being killed so it hides. In a way, a shy child is shy of people because they look dangerous or intimidating. A shy adult is feeling a sense of that fear or vulnerability.
Some shyness is just not fear but a personality trait, like introversion. Being introvert doesn't really mean someone is also shy.
Shyness is a form of embarassment too. A person can be shy of wearing a certain type of clothing because they don't want to look stupid.
A shy sense of being phobic of other people is social anxiety or it can be avoidance personality. I'm like this and it's because I feel drained being among people. Listening to people chattering all day gives me a headache especially when they talk a load of rubbish.
I was in the darkness so darkness I become.