Shy guy, awkward stares and dorky grins. Does he like me?

We had a thing 6 months ago that fizzled out. Recently he has drifted back into my life and it is all over the place. At times he can't keep the grin off if his face, other he's solemn and quite, others he's cheeky and in my face and more and most recently he's shooting glances in my direction constantly to the point where it is like he is watching me.

My gut says yes, but he's uncertain or something. What can I do besides smiling at him to make him feel comfortable enought to strike up good conversation with me when there are other people around?

He's sat at a table with me and three other people last week and though he spent most of the time glancing my way...didn't speak to me once. Every time I tried he'd get quite.