What does it mean when a guy stares you down from a distance then will not look your way when close up?

He's probably shy. Or, he could be far sighted.
He is a very confidant person
If this is a guy who you really know, like a friend, it might mean something is up. It could be trifle, like he is mad at you. But usually, eyes are the giveaway of a drug taker, and that is very serious. Or, if he is a guy who might like you, he is just nervous!