My 2004 is doing the exact same thing except on the driver's side. The previous owner had a minor wreck and the front bumper, driver's side fender were replaced and the front driver door fixed. I'm thinking they didn't replace the hub/bearings on the driver's side when repaired. The vibration and slight humming noise is a common indication of the hub/bearings going bad. If you have had your tires recently cared for, I'd have the hub assembly checked. You can jack the tire of suspected issue up and push on the top and bottom of the tire. If there is a good amount of movement/play, then the bearings need to be replaced. Keep us posted on anything you find out if you don't mind.