WHY DOES HE DO THIS?

Whenever I see my ex, at first, he won't make eye contact, but then I will see him looking at me. At first, I think I'm paranoid until we continuously make eye contact and then we both quickly look away. Then, he seems to be laughing louder or talking louder and being more goofy and trying to be funny and when I talk of laugh he will occasionally look at me or listen almost intently. I even had to walk off for a minute and I saw him glance up at me a few times on my way back. I thought he was looking at my friend but she sat next to him and he hardly spoke to her and didn't even look up.