My Nikon D7000 has randomly started making me have to press the shutter button twice?

My Nikon D7000 has randomly started making me have to press the shutter button again after i've already taken a photo?
I think i might have pressed a button or something but every time i take a photo the shutter sound doesn't fully finish, and the screen goes black, so i have to press the shutter button and the shutter sound finishes and the screen isn't black anymore, this hasn't happened to me before and i really need to get it sorted! Please someone help

Check that you haven't engaged the mirror lock, and that your shutter-speed/aperture settings are in mid range (an old one is the aperture ring taken off its minimum setting) and that your ISO is high enough to suit the conditions.

If your camera has a, 'T,' setting, make sure it's disengaged (rare on modern cameras, but it can be useful).

If all else fails, reset the camera.

Since the Owner's Manual can be difficult to understand, watch this video tutorial:
http://www.nikondigitutor.com/eng/d7000/index.html Who better than Nikon to teach you to use your Nikon D7000?

It sounds like you have Live View activated - when that's switched on you have to press the shutter button twice to take an image.

There's a button on the back above the multi-selector button - turning the lever to the right activates Live View - turn it back to the left to switch it off.

As Andrew said, it sounds like your Mirror Lock is turned on.
I'm not familiar with that camera but there's probably a setting in one of the menu panels where you can turn it off.

Andrew probably has the right answer but it's strange that this is a random occurrence.
See pages 7 and 83 in your manual.
Keep your release-mode dial set to "S" for normal shooting.

Otherwise, try a reset on your camera.
See page 151 in your manual. Alternate way to reset is page 202.

Another reset is your menus.
Bottom of page 207.

Doing both the above resets will pretty much take your camera to factory mode.