Question PC suddenly restarted for some reason

[Borko1]

Hello. My computer restarted a while ago when I was surfing the net. It didn't even do a full restart, screen just turned black in all of a sudden. Monitor LED was blinking, keyboard and mouse colors were messed up at first then later they stopped working and long press power button on the case didn't work at all. PC didn't want to turn off, so I had to switch the PSU button. It's working now like it has before (as I am writing this from this PC), but this is the first time of it happening, so that's the reason I was very worried and immediately went seeking for help. It could be anything, but my suspicions (in the most-likely-possible-failure order) are PSU, CPU, motherboard and maaaybe RAM. PC parts are not pretty old (1-2 years old) and I've been upgrading them over time. The only part that I will definitely change in a close future is this trash and cheap 400W PSU which doesn't even have a brand. I think it is most likely a cause of this problem, even though it did it's job perfectly over the last 2 years, it perhaps slowly approaches the end of it's life. Here (click) you can see my PC specs and idle temps. Thanks in advance.

 

[scout_03]

use occt and stress test psu for about 10 min take not of voltages before and on test report result

 

[Borko1]

use occt and stress test psu for about 10 min take not of voltages before and on test report result

I couldn't let it burn for 10 minutes. After a couple of minutes, the CPU began to rapidly increase temperature, it had 83 degrees Celsius at 100% usage and it was still rising. However, I did manage to take photos of voltages.
Pre-Test
During-Test.

 

[scout_03]

first do a cpu cooler repaste and clean dust in fans also what is the case name and model and king of air flow you have in case fans system overheath .

 

[Borko1]

first do a cpu cooler repaste and clean dust in fans also what is the case name and model and king of air flow you have in case fans system overheath .

I will do a repaste when I order a thermal paste, because right now I don't have one. PC case, as well as PSU, was made by some local brand from my country, which uses foreign parts (mainly Chinese) and I got them together for some cheap money. I am new to that air flow thing and I don't know how to determine it, I have only 2 fans in my case (CPU and PSU) and temps were never a problem until now when I ran a stress test (CPU was never at 100% usage and max temps when gaming were 60 degrees Celsius). Now, I got to mention, I am not on a very big budget, so I am trying to build a medium-budget PC. As I said, I will definitely consider replacing this PSU very soon and I am thinking of upgrading the GPU too.

 

[scout_03]

we will try to have this one work for now and upgrade later when budget be there could you link to the case name and model will see if we could do something .