hmmm your gtx 970 specs require a PSU of a minimum of 500W / 550W by specifications (depending on brand).... so you might upgrade that for starters. plus when you're really using it it's going to tax your system... with whatever cooling fans, hard drives, extras you have. the gtx 970 is a high-end board. I wrote a post somewhere else on here about having 2 hard drives burn out with a PSU that wasn't up to snuff (even though it was rated well above minimum power levels).
the 5 second 'spin and stop' to me sounds like the obvious 'immediate shutdown for cpu or cpu cooling fault (which would be the bent pin/short/ or missing cpu fan connector --> like the cpu fan not plugged into the sensor header on the motherboard so the motherboard doesn't know the cpu has a fan installed) [boards w defective but not shorted cpus can just have the fans just spin on max speed.. and not pass the POST.]
depending on where you bought your setup, some stores are notorious for just putting returned (aka defective motherboards) back on the shelf for the next person, but 'the egg' is usually pretty good. and I've had great experiences with Gigabyte boards, they're solid usually, but a bad board does happen from time to time. some stores will test the board for you if you ask (or if you buy the mobo, ram and cpu, can test the setup there)--> or you can just swap out the board. 2 bad boards is much less likely (just don't get an open box item).