My iPhone 5's camera freezes whenever I open it.

When I open the camera app, it just shows the closed shutter, with the normal functions on the bottom (button to take the picture, and the switch to camera/video option.) I can't select any options though, they are greyed out. I tried waiting a little bit to give it time to load, but it will literallt last minutes. I've restarted my phone a couple times but it came to no avail. Is there anything I can do about this problem? Is this a common problem?