My Nikon D3000 won't auto focus anymore?

I've tried holding the shutter button down halfway and everything. Yes, it is a AF-S lens. I've even restarted my camera to the factory setting. Every time the lens are on auto, and I press the shutter button, halfway and all way, it'll keep trying to focus. But when it focuses, it goes from really blurry, to still blurry, to perfect, to blurry again. How do I fix this? Yes, my lens are on correctly.

It might be trying to focus on to many focus points try changing to spot focus in the menu & see if that works, I have a D90 & that happens to me sometimes, either that or use manual focus.

Do you have plenty of light? Do you have vertical lines with enough contrast?

It sounds to me as if the camera simply hasn't got enough contrast to focus with.

Try it outside during the day, and pick a subject such as a truck, car, windows on a building, some flowers… Anything with good light and contrast. That will narrow down what is going on.

I does sound like you are trying to take photos in an area too dark for your camera to find a focus point

The fact that the images are blurry, probably means that the shutter speed is too slow and camera or subject movement is causing blur

What you are calling "blur" is actually called being out of focus. The fact that the lens is hunting for a focus point shows that you are shooting in a dark place.

Make sure that your auto-focus assist lamp is on.

Page 122 of your user manual explains how this works

Lock the lens fully when you put it in.

Release the lock button, don't touch it.

Turn the lens clockwise until it won't move anymore. Bet this does it emoticon. It goes away over time.