Okay, so here's the thing you should know:
The CPU + GPU + Motherboard and other power hungry parts (most items that use Motherboard power like case fans) usually share the "+12V1" or "+12V" section of PSU railing.
Your "+12V" or in this case "+12V1" rail is rated for 180W (12 Volts multiplied by 15 Amperage.) That means you are limited to 180W between your CPU + GPU combo (in theory) without tripping OCP (OverCurrent Protection), 192W if you want to use the "12V2" section for arguments sake.
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Your RX 570 is rated to use 150W when its being fully utilized. Your CPU is rated to use 65 Watts at its rated base clock of 3.40 Ghz. Between those two you are looking at ~215 Watts at load without any overclocking to the GPU.
At load you are pulling 215 Watts sustained out of the maximum (180/192) Watts the PSU (+12V1/+12V2) railing can supply. Gaming spikes your power usage at times to 265 Watts, probably where you would see your PSU shut off and reboot your computer if it hasn't done so immediately.
You definitely want to upgrade your questionable, no named Power Supply ASAP if you want to use that RX 570. That or step down your GPU to a ~75w card (i.e. 1050Ti or RX 560.)
You are probably using a pre-built PC from a while back, with the expectation of upgrading the Graphics card to get a better gaming experience. Perhaps for yourself or your child. I bought a pre-built a couple years ago and swapped out the power supply ASAP.
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For example, this is my current PSU:
The +12V is 42 Amperage (12 times 42 = 504 Watts), which limits my CPU + GPU to around say--- 300 to 375 Watts total. This gives 125-200 watts for my other power hungry parts to use.
I am running an Intel i5 6402p and an RX 580 8GB Reference.
My i5 draws 65w and my RX 580 draws 185 Watts. Total of 250 watts or so at load, with a 250 watt of headroom for the rest of the PC to use (Motherboard, Case fans, Hard Drives, Solid State Drives, Peripherals, etc.)