[Nocap]

Shyness is only one possible product of introversion. It's not a guarantee. My INTP friend is more outgoing than I am, and I'm extraverted.

The Shyness of an introvert is only the result of their favoritism toward developing their own subjective interpretations (doesn't matter if it's Thinking, Intuiting.. as long as it's an Xi function) of the world, rather than actually dealing in the world.

Like dissonance said, it's entirely dependent on whether your first preference, feeling, sensing, whatever it is, is introverted or extraverted.

The shyness you're talking about might come from an introvert who's not quite confident in his introverted ideal and wants as little interaction with the world as possible because it continually skews the internal model. That's why introverts often prefer to be alone, but if you've got an introvert who IS confident in their own impressions, then they'd have no problem acting, and might not be shy. But they still also might be, if they happen to just naturally not be a social person, and instead spend their extraversion time with objects or toys or... whatever else -- not people.