What Do I Do?

Hey guys.

I work with a man who is 44 years old, I’m 22. He’s okay I guess but he literally gets into these odd moods which I can’t describe. He acts silly, but I think he does it purposely. It’s like he intentionally tries to annoy you. Does this make sense? Like, I’m a sensitive person but there was a book in our store with a group of people on it and he pointed out this weird looking guy and said “that’s Sarah”.. He then started sneering and laughing. I started to act a bit off towards him and he knew that. I was getting on with my work, wasn’t looking in his direction etc. When I was heading for lunch, I clocked out and he was right beside me.. I had that feeling that someone was watching me and I looked up, he was just staring. When I caught him I said “what?”, he shrugged his shoulders and replied “nothing” and just laughed. I continued to walked out of the store. I don’t know if it’s me being overly sensitive but sometimes you don’t know whether to take him seriously or not.