What if a guy sometimes ignores you but looks at you often?

In cl if say say were talking in a group and I'd say something , he wouldn't always really respond and just look. But answers a bit when others say something. Then when I speak to him myself he gives full attention listens closely and doesn't get distracted and seems friendly and adds things in to what we were talking about. I usually have to start it. He always seems to stand around me or beside me and doesn't talk around the same particular cl. In the hall he looks over at me alot I also look at him too. Maybe hes looking cause he knows I look? I've tried not looking and seeing if he looks over out of the corner of my eye and he still does.Neither of us smile. He walks close behind me, in the hall I'd left with my friends him and his weren't far behind , I wasn't near him, when I reached the end of the corridor I realised he had gone close behind me. So I'm confused hes a really nice guy but he only talks to me really if I talk to him first when hes alone. In a group he won't say alot. He watches me speak to my friends though and when I smile . I'm confused about him I think he might. Hes a quiet guy but in some cles the one where he stands near me alot he seems more talkative in cl, can be quiet though. Hes kinda subtle about it. Hes not a flirty sorta guy either.