When a camera is pulsing back and forward it suggests it's not finding focus. Usually that is because it cannot get a clear focus lock within the focusing area. That could be caused by insufficient light or the lack of contrast within the focusing area.
What lens or lenses are you using and does this happen with only one lens or with all of them?
Have you done any customization of the camera setup?
One thing you could try straight away is to reset the camera to defaults, in the wrench menu.
cheers, TREVOR
"The Amount of Misery expands to fill the space available"
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
