Can strangers decipher this strange behavior?

There's this contractor working in my office building and
For the past 3 months, I run into him maybe 2-3 times a week.
On the days I run into him, (hallway, elevator, etc.) it's usually 2-3 times in the same day.

Once or twice, I had a conversation with him, asking how the construction was going. He seemed friendly enough, answered and that was that.
I don't flirt with him that I am aware of and we exchange a hey or hello when we see one another.
Lately I've noticed he started to seem a little awkward when he sees me.
He will look at me quickly and say hello, look down and then hurry off.
There are times were we pass one another and a side smile happens but I've also noticed most of the time he avoids looking at me. He will look down as he passes me or just look straight ahead to avoid eye contact.
Later that day, we run into one another and he says hi shyly and looked down, on my way home, I got on the same elevator and stood across from him and he completely avoided looking at me. 25 flights down and I would glance at him, but he would be looking at every direction but mine.
As I got off he said " haves good one".
I'm assuming he has no interest in me but when he acts like a shy school boy, it confuses me. Thoughts?