I love my wife, and I no longer know if I want the marriage

Dear Delyara, My wife and I have been together twenty years. There is no affair, no abuse, no dramatic betrayal. We are kind to each other. We divide chores. We still laugh. And for the last year, I have been wondering whether I want to leave. I hate the absence of a clear reason. If she were cruel, departure would have a story. Instead, I sit across from a good woman eating soup and feel a quiet desire for a life that does not include explaining where I am going. Then she reaches across to wipe something from my sleeve, and I think I must be insane to risk this tenderness. I have not told her. She is planning a trip for our twentieth anniversary. I help choose hotels while privately imagining separate apartments. I do not know whether this is a midlife crisis, depression, buried resentment, or simply a marriage that changed shape without either of us noticing. Love is still here. That is what makes the confusion worse. I thought wanting to leave would require love to be gone first.