i have the same problem with my 10700K on 2 different boards and i cant figure why and how to fix this...
1st board Aorus Z490 Elite AC
2nd and actual board Asus Strix Z490-E Gaming
i overclock it to 5.2Ghz, in windows everything is fine no BSOD, after restart in windows is at 4.8ghz despite the 5.2 core ratio set in bios....