My wife has had better days. How can I get physically attracted to her again?

Talk to her. We have all had better days. We all age as times goes by. Some us try to take better care of ourselves. Tell her you want to be attracted to the woman you married. Let her know you think about her.
Wife and I. The things you bring a relationship together is not always the same that keeps it together. Trust and open communication is usually what makes a relationship intimate. Respect for each other is another element that improves intimacy. And when you have intimacy many other wonderful things happen from here. So start by speaking your need.