Phone shuts off automatically when I let go of the power button.

The only way to make the phone stay powered on is to hold the power button on the phone. As soon as I let my finger off of the power button, it shuts off. Battery is over 80%, and whether it is plugged in and charging or not this issue persists. I've removed the battery, checked the pins and replaced it, the problem has not been solved. Anybody have any ideas?