Why does this guy act so weird around me?

[Anderson]

So there's this guy at my work, maybe a year or two older than me. We don't work in same sections of the store, but I can always see him from far across the room, and every time I look at him I see him looking back, and I somehow always seem to catch him look at me and then quickly look away. We haven't talked before, so I decided to add him on Facebook just to try and start a conversation, but he never did anything about the request so I forgot about it. Since then I still catch him looking at me, but even when we have the opportunity to talk for instance in the break room, he wont say anything.. Why would he act like this? Also I think both of us are pretty shy, so it's hard for me to just go up and make the first move because I'm afraid he might not be interested. What should I do?