Question PC keeps rebooting when loading into games

[Funsize1324]

Hi,
I recently bought a used Rx 580 from eBay for a good deal. I realized it has been mined on with a modded bios so I just flashed it to stock no problem, however when ever I load into a game my pc reboots without any warning. Sometimes I get in and can play for a few minutes then crashes. This only happens in games. I bench marked Unigine Heaven and it worked the whole time. I tried monitoring the power and voltage when it loads. Everything seemed fine. Temperatures are fine, staying below 75 degrees. I wonder if its a power supply issue since I have a 10 year old cooler master PSU from my dad. My specs are:

G4560
B250m Gaming Pro
XFX RX 580 8gb
2x4gb Patriot Ram 2666Mhz
Intel 660p 512GB
Cooler Master 600 watt power supply

 

[010010]

I would look to it being a PSU problem as you suspect. I had a similar experience with a new graphics card that was fine until I loaded into a game/played for a while. The extra power draw would cause me to have the same problem.