New PC won't boot, just restarts after 20 seconds

Mangostorm

Commendable
Dec 27, 2016
1
0
1,510
New to the pc game. Built my first build a week ago. Have tried as much as I can without forking out another few hundred pounds to replace parts to test.
When I connect it to power and try to boot it, it boots as if it's fine but after exactly 20 seconds each time, it restarts and so on.
My build consists of:
-Gigabyte ATX B150-HD3P
-Intel core i5-6500 3.2GHZ
-Msi gtx 970 graphics card
-16gb of memory from 2 8gb ram
-PSU Rosewill Glacier 600w
-Seagate barracuda 2tb hard drive
-Samsung 850 evo ssd

Have checked that all cables are in fine, all part are correctly installed.
Is there a next step or is the next step to replace parts until it works, which I'm not looking forward to as I'm already way over budget