Annoyed, guys what's the deal?

theres this classmate, who I don't personally know but doesn't seem to be shy at all as I've seen him be pretty talkative in class and talks to some other girls. ealrier in the year it seemed like we'd maybe start talking, id see him looking at me and id look back and he finally talked to me once (it seemed like just an excuse to talk Because it was random) but then not again. in class I've tried to make myself seem approachable, smile at his direction and he looks but never talks.

what sucks is there's literally never been another good opportunity to talk, but like I said he doesn't seem shy and he did it once so I guess I'm just askking, does it seem like I was just mistaken and he's not interested or maybe he's actually shy or intimidated ? I've never really had a good grasp on how guys flirt (ill think a guy is interested but he's not, or think he isn't interested when he is, sorta thing lol)