Why does my nikon d3100 shut off as I'm taking photos in Manual and Shutter mode?

It just randomly started to happen and it makes the photos I take look as though they're over a decade old. Please help

Added (1). My camera is in auto mode currently and i'm not so sure what shutter priority mode is. I also notice that "job nr" flashes at the bottom of the view finder as well as "auto" below "iso". Again.

Does it happen in Auto mode and shutter priority mode? If not, then it's just you're settings. If yes, then check white balance and set back to Auto. If it continues to happen, send your camera in for servicing.