Every extrovert is an introvert in some way. I have seen introverts become extroverts in their comfort zones and have seen extroverts become introverts in a new and unfamiliar environment or situation.
My problem was that I just couldn't get outside my comfort zone. After years of forcing myself outside my comfort zone (which many people don't or can't do), I don't really have a problem anymore.
One of the problems with being introverted is that you will probably get passed up for promotions at most companies. you need to be social to move up the ladder, even if you are a developer.