Someguyuphere Unfortunately that sounds as if it might be a hardware failure. It would be prudent to save important data as soon as possible.
Though this would obviously be very disruptive, you could differentiate between hardware and software by (after backing up your data) flashing the device back to Google's stock OS to see if it continues to suddenly power down.
As a possible intermediate step, you could investigate a potential corruption of your user data by trying out a "factory reset" (which would permanently wipe all of your data). Was the device recently run down to 0% battery?