Question Need Help. My CPU is overheating constantly

[Incidious_xo]

I recently built my new gaming computer and have already run into a problem, at idle my PC runs at 60C and when I start playing games it almost immediately starts throttling to 100C. At the moment I borrowed a friends Intel stock cooler just to keep the thing cool and plan to upgrade soon I am just not sure why the thing is so hot. Is it because of Intel's thermal paste? I am not sure but I installed the NZXT cam software and noticed the CPU clock speed is adjusting itself constantly for what seems like no reason. Going from 800Mhz to 4200Mhz in under a second then dropping back down immediately afterward. I am just confused and am looking for suggestions on how to fix it. Btw I also have only my CPU in my computer at the moment but plan to get my GPU soon.

 

[rgd1101]

because the stock cooler can't handle your cpu?
full system spec?

 

[Incidious_xo]

because the stock cooler can't handle your cpu?
full system spec?

MSI Z370-A PRO MB
I5 8600k
Silverstone RL06 Case
EVGA 650 GD PSU
G.SKILL Value Series 16gb ram 2666mhz
Kingston 128gb SSD
WD Blue Edition 1TB HDD
Intel stock cooler
I think that is it (haven't decided on GPU)

 

[Incidious_xo]

I am also not even overclocking the CPU so I am stuck

 

[Karadjgne]

Not all Intel stock coolers are the same. What cpu did your friend have that the cooler came with? You have a 95w cpu, if your friends cooler was from an old cpu, it could be too small for the job. For instance my i7-3770K is only 77w cpu. If you used my stock cooler, you'd have overheat issues for sure.