Nikon D3000 stuttering problem?

Ok I'm not sure how to descirbe the problem but basically when I turn my Nikon D3000 on I look through the viewfinder and the image stutters in there as if the lense is aligning or something. I don't know if this is normal or not but it didn't always do it so becoming a bit concerned i thought i might need to buy a new lens. I'm not really sure how else to decribe this I don't know a whole lot about cameras. But thank you all for your time.

Added (1). Http://forums.dpreview.com/forums/readflat.asp?forum=1034&message=35592052&changemode=1

This person describes what I get aswell.

That's the autofocus system looking for an object to focus on. If you are in the dark, that should explain the problem. You see, what is low light to you may as well be pitch black darkness to the camera already.

As previously stated, that is the camera having difficulty autofocusing. You're 1) trying to take a picture of something too close to the lens 2) Taking a picture of something too dark or 3) trying to take a picture of something the camera can't recognize, such as a white wall.

It should not do that unless you are depressing the shutter button half-way.