Sometimes the metal shield behind the rotor get bent or rusted and hits the rotor. Probably not whats happening here. Finding the problem requires diagnosis techniques, and visual inspection. Does turning left or right affect it? What about braking?
Good think to do in testing. If a bearing is failing activating the disk brake calipers stabilizes the rotation and changes the behavior of the bearing. The real test is to jack it up (safely) and then test the bearing play and inspect the retention nut.