Mystery Attraction

I'm a professor at a university and I've always been content with my single life. But lately, there's this student, let’s call him Alex, who has caught my attention in ways that are entirely unprofessional. It started with his keen interest in class discussions and gradually escalated to me noticing how he looks when he smiles or the way he carries himself. These thoughts should be unacceptable, but here I am, struggling with them. Is it wrong for a mentor to have such feelings toward a student? How do others navigate these boundaries without compromising their integrity?