I'm in the exact same position. I would love to be in tv shows and really develop a character, but I'm a pretty withdrawn person. But then I remind myself that there were and are a lot of celebrities that are introverts and they're great at acting. So don't worry about being shy, you do have a script after all. :)
As far as actually getting into a tv show, any film in general, if you don't have much experience then it's best to start from the beginning. I have no experience what's so ever. What I do is simply take some scripts from a movie or a tv show and pick a character to play. I'll look stuff up about acting for the best advice (Btw, this is a really good site:
link) Once I think that I have a hang of it, I plan on going for a few plays to get to some experience and then to try going for commercials. They're the best to use to break into the business.
Hope this helped!
