Don't worry, I've been there and improved gradually. Watch my latest video and compare it to my latest video. You might get motivated how much I've improved. xD Don't be demoralized if someone gives you a feedback. YouTube is a great help for building confidence.
I found I was pretty shy for my first few videos, but the more you practice the better you get. Try saying what youre thinking aloud when playing a game. If you still find yourself to be too shy for sure try doing more co-op things if you can, until you get used to talking in videos, then try one by yourself.