The GPU, as you suspect. Or, it could be your power supply failing in some way. Or, something wrong with the motherboard. Each of those could exhibit the symptoms you're describing.
The easiest way to test a GPU is to put it in another machine. The easiest way to test a power supply is to swap it out. The easiest way to test the motherboard would be to put a different GPU in it.
Each of those is difficult for a home user to test, because few of us have spares sitting around. Maybe you can call repair shops near you and see what they'd charge to run just those three quick tests for you, and not a full troubleshooting session.
First off specs.
Corsair RM840x psup, Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz (8 CPUs), ~3.5GHz, 16gb corsair ram, Samsung SSD 850 EVO 250GB, SanDisk SSD PLUS 240GB, PNY xlr8 GTX 1070, Asus ROG Hero VI mobo
Recently we had some thunderstorms on the horizon so I thought I would be proactive and unplug everything while I was gone for the day. When I came back home and plugged everything back into the wall my first boot up was very loud fans all maxed out and no video. My next boot it restarts multiple times. sometimes the led light says vga led sometimes it says boot led. When I unplug graphics card and just run thru the mobos onboard it runs totally fine. ive tried the different pciex spots and it does the same thing. I even ran a game overnight via onboard and it didnt get that hot didnt restart or anything. the graphics card is less then a year old and seems to have the fans spinning and running fine also. this all seems to have stimmed from me unplugging it from the wall and back in. Im calling the pny support for their 3 year warranty because the card is not even a year old but I just dont want to waste time and ship it all the way out if thats not the problem. Also cant really afford to just buy another card to test. Thanks for your help