Well, shy guys will not initiate anything unless you tell him about your feelings for him. For shy guys the fear of rejection is much greater than for any other guy and they typically will question whether the girl is truthfully flirting cause she likes him, just playing him, or she is just a natural flirt...shy guys can't always tell.
I don't know if you are comfortable asking a guy out...especially shy guys. As a shy guy, I love it when a girl is straight up with me and not just constantly flirting. I remember when a co-worker of mine had constantly flirted with me, and I really felt she liked me...but realized she had a boyfriend 8 months later (I was totally pissed at her, but never told her). Us shy guys cannot pick that up.
Don't get me wrong, I don't mind approaching a girl. She just has to be single and be interested in me. They say actions speak louder than words...but not this time. You can do all the action you want just short of grabbing his crotch, but telling him is the most effective way to clear the air. Trust me, shy guys LOVE bold woman who are upfront...I know I certainly do.
If you do decide to tell him, tell him in a one on one setting where you know you won't be bothered by anyone (say a park or a quiet room with the door closed). Make sure you touch him when you tell him because touching is extremely powerful. When you touch someone they remember what you said more and will feel more at ease with you. But MAKE SURE you touch him in a unique way that you wouldn't touch anyone else...make him feel special when you do it. Otherwise you'll lose him. So you can wrap your arm around his arm and clinch his hand on the arm that you wrapped with both your hands. VERY POWERFUL. That's what I would suggest. Let me know how it goes!