My Nikon D3100 won't auto focus?

So I bought a Nikon D3100 around 7 or 8 months ago and till yesterday, I had no problems with using it. However, yesterday when I grabbed the camera to take a picture I realized it couldn't focus on anything automatically. I didn't insist on the problem and took the photo manually but today I saw that it wasn't a temporary situation. I took off the lens and placed again but didn't it solve anything. I behaved my camera very well and I swear I didn't do anything that I think could damage the camera. And I'm using the standard lens comes with the cam.

What might have happened? And what can I do? I purchased it from Abu-Dhabi so I assume the warranty isn't valid here in Turkey?

Call Nikon and ask them for some help.

800.NIKON-UX.

What you are experiencing is nothing that I have ever experienced with any of my fully adjustable cameras, Nikon, Canon, Leica and Hasselblad

On the lens, there's a M/A - M switch. Make sure it is in the M/A position. You may have inadvertently bumped the switch by accident.

This switch puts the lens into Manual/Automatic or Manual focus mode.

If that is not the problem, look in your manual for any other ways to put the lens into Manual focus mode, such as a menu.

And finally, if neither do not apply - look for the master reset in the manual. Perhaps the camera just needs reset.