... i9 9900k ... DeepCool GAMMAXX 300 ... 50-60 C idle OC 5ghz ,and 100C in Cinebench ...
Just FYI, your cooler is only marginal for a 4 Core 4 Thread processor at stock settings; not an 8 Core 16 Thread processor under any circumstances, let alone overclocking. Moreover, your cooler uses the same problematic "push-pins" that Intel stock coolers use, which are notorious for being deceivingly tricky to get the pins fully inserted completely through the motherboard and securely latched. Push-pins cause a disproportionately high percentage of problems with high Core temperatures, which may be the reason for your high idle temperatures.
Until you can replace the cooler with a solution that's as appropriate as your case constraints allow, you can test for a loose push-pin by watching your Core temperatures while you push down and hold each corner of the cooler for about 30 seconds. When you see your Core temperatures drop, you've found an improperly seated push-pin. You can also check the push-pins by closely and carefully examining the back of the motherboard using a strong light and an eye for detail. All four push-pins should appear to protrude equally, with no differences between any neighboring pins.
It is
not recommended to overclock using “Auto” BIOS settings or motherboard OC tuning features such as MSI Game Boost, as significantly more Core voltage than necessary is applied to maintain stability, which needlessly increases Power (Watts) and Core temperatures. It's instead
highly recommended to use only "manual" Vcore in BIOS. Most overclocking guides explain how.
CT