For most of my life I did not realize I was an introvert until after having a discussion with a friend about what I would rather be doing than *insert group function's name here.* Once the realization hit me, somewhat of an emphany, I was dragged into an extended period of self introspection. I started inventorying life experiences and specifically regrets that were impacted by my introversion. Among those were of course my fear of rejection from women. I am not sure I have ever asked a woman out, even to this point in my life. Most of my encounters and relationships were intiated by others, girl, woman, or a third party (p4p excluded and even that has its own anxieties attached) rather than from mustering the courage to do so of my own volition. However, I have come to the conclusion that introversion has nothing to do with my fear of rejection, but rather it's protecting my pride and ego.
I am my own fan club, never have I ever not believed I am incapable of doing anything I set my mind upon. However, I have always increased my odds of success by controlling variables to stack the deck. And therein lies the difficulty, I know I am not an attractive individual and I recognize that fact. Therefore I am afraid of injuring my pride via the obvious rejection I will receive, most likely the "I would just rather be friends" response, which can only be taken in the most harshest way possible (not interested in you, but I also pity you too much to be candid).
Could introversion stop someone from asking someone out, yeah maybe. But I would think it would depend on the setting, but I do better one-on-one, and since it only takes two to tango, well. For group activities I don a persona, who would want to date my persona?
But Hana, seriously, if it is pride, then you fail to recognize what many of us know, you are a breathtakingly beautiful woman and person. I would have to echo previous comments, they guy (or girl, sorry had to have a little fantasy, it's my post afterall) has other issues that have nothing to do with you. My goodness, if you had approached me at your age when I was a much younger man I would have been floored and looking for the hidden camera.
Perhaps if you still feel it is because you are shy, try to control the setting to an environment that makes you more comfortable. And please accept that if you get rejected, they have their own issues, and you are probably better off not learning first hand why they are such idiots.