That error is hard to track down and most diagnostics do not discover any problems.  

I had that and it turned out to be a i7 3770 CPU problem and the Intel CPU diagnostics did not detect any error. I did a "shotgun" approach as I do computer support and had spare parts.  Swapped power supply then the motherboard and finally the CPU and after replacing the CPU the problem was resolved.  Intel replaced the CPU under warranty.  I've helped several on other computer forums with the WHEA error and they all turned out to be CPU.  This does not say your problem is CPU, could be the video card however, the only real way to find out is to replace it with a known good video card.  The same way with a CPU problem sadly the only way to find out is to replace the CPU.

This doesn't "fix" your problem but proves my original statement about "hard to track down".

According to the Dell documentation this has an HDMI port on the back I/O panel.  It says if your PC came with a video card that is covered. If the cover is removable and you have a monitor with an HDMI port or even a TV with HDMI that you can use for testing you can remove the video card and use the HDMI port.  If there are no WHEA errors then that most likely is the Video card.  But if you continue to get the WHEA errors its very possible that the problem is the CPU. 

WHEA_UNCORRECTABLE_ERROR   PHYSICAL HARDWARE FAILURE.

Once you add-up a new 330w AC-Adapter, GTX-1060 its probably fine.

Vendor 10de. Name: NVIDIA Corporation.

Your GPU overheated and is now Bad.

0x13c0-0x13ff     GM204

EVGA.GTX970.4096

https://www.techpowerup.com/vgabios/162035/evga-gtx970-4096-140905

GPU Device Id: 0x10DE 0x13C2

Version: 84.04.1F.00.70 GM204

VBIOS (HWDIAG)

Copyright (C) 1996-2014 NVIDIA Corp.

GM204 Board Connectors

1x DVI-D

1x DVI-I

1x DisplayPort

1x HDMI

Board power 187.0 W

My Alienware X51 R3 is having the same problem. Dell had changed the motherboard twice, but the problem remains.