Camera turns off once shutter button is pressed.

The camera, at any random moment in use, turns itself off when the shutter button is pressed. Focus points light up, camera focuses and sets exposure, but camera turns off instead of taking the picture. The only way then to turn it on, is to remove and replace the battery. I've tried resetting camera settings, various modes, charged battery, and have even used different lenses but nothing is solving this problem. Got any ideas??