What causes shyness?

Is it a trait that someone just “is”—that person is always shy, always has been, always will be.
Or is it something we grow into?
Out of?
And is shy the same thing as quiet, as closed off, as avoiding attention?
What would make a loud and wild person become timid and shy? Could anything?
And what would make a shy person come out and be seen?
Are you shy? How shy? Why? Do you wish you could change, either more or less so? Have you?
Is that enough questions rapid-fire? lol : )