Hi Ruth,
If you have noticed that he always tries to be the center of attention when he is at work, not just with you, but with other employees, he may simply be having fun with you. In essence, he likes the attention and not you per se.
However, if you have noticed that he only tries to get your attention and no one else’s, he may like you. That would mean that all the staring that he has been doing is due to attraction.
However, whenever you have asked him about why he is staring at you and he would say nothing, that may mean that to some extent he may be too shy to express how he feels to you.
It may be easier to get him to express how he truly feels about you if you were to start having conversations with him about topics that he is really passionate about.
Doing this over time will help to build trust with him and this is often what could make him feel more comfortable with expressing his feelings to you at a point in time.