You know that, no doubt. All day long, a vague melody runs through our heads without us knowing where it could come from. We whistle it mechanically, until it becomes frankly annoying, and then we finally find the title, relieved.
I apologize to readers who will have this look in their heads because of me. The song in question was I have a problemsung by Johnny and Sylvie, a slow song from the seventies that I hadn't heard for ages, even in the background: “I have a problem, I feel that I love you/Oh, I have a problem, it’s that I love you too”