Question i7-10700K random clock speeds at startup, HELP?

Aug 1, 2021
New to PCs, def CPU behavior, so bear with i7-10700K normally posts with a 4.9 GHz clock, but every once in a while it will boot up running at 5.1 GHz and will immediately thermal throttle during load/stress testing. At first, I thought it was my AIO not functioning properly, all I saw was the CPU temp spikes and throttling, not noticing the higher 5.1 GHz clock speed. But aren't CPUs supposed to vary clock speeds within the given specs depending on load/task, not stay stuck at one particular clock? Anyway, I kept remounting my AIO each time it happened telling myself I was mounting the AIO wrong or air was in the pump until I finally noticed the higher clock. The base clock is 3.8 GHz and boost 5.1 GHz per specs of this CPU, so is it just getting stuck at max boost or something during boot up? At 4.9 GHz (its normal operating clock 98% of the time) it will maybe hit 78-80C in a stress test, running steady at 60-65C during heavy gaming. but every once in a while it will start up running at 5.1 GHz and overheat immediately. Anyone know whats up?
System specs:
GB 3080 Ti
32GB DDR4 @3200 MHz
Aorus Z490 Elite AC

Thanks for any insight!