Usually caused be a secondary device. If you guys have a cable box try this test. Unplug the coax cable from the back of the cable box. plug the coax cable from the wall directly to the TV and do a chennel scan. See if the probelm is still there. If it is TV needs service. If it is gone...it is your cable box. Call the cable company. If you have Satelite all you can do to test it is try another device and see if you have the same problem. A dvd player, VCR, game console etc. and see if the problem happends with that as well. If it does then the TV needs service.