The CPU temperature and usage are suddenly surging and fluctuating. Before the 1003 BIOS update there was no such problem. How can I fix it?
BIOS : 1415
MB : ROG CROSSHAIR X670E HERO
CPU: AMD Ryzen 7950X3D
RAM: GSKILL 64GB (2x32GB) Trident Z5 Neo RGB 6000MHz CL30 DDR5 1.4V AMD EXPO (F5-6000J3040G32GX2-TZ5NR)
PSU: ASUS ROG Thor 1000W Platinum II
GPU : MSI Suprim X 4090
Arctic Liquid Freezer II - 360 A-RGB
Are you sure this isn't just normal system operation? I.e. some task or service just using the CPU. Temperature is expected to surge/fluctuate within normal limits when the CPU is under load. A short usage (and temperature) spike isn't particularly unusual when Windows or some installed software decides to do something in the background.
It really depends on the numbers you're seeing. Under heavy load, the higher end Ryzen 7000s can easily sit at 80C+, or even hit the boost limit of 90/95C under extreme loads (like benchmarks). That's even with a 360 AIO.
Under lighter loads, you should probably be seeing idle temperatures in the 40s, but rising into the 50s or 60s under a bit of load. A single thread that pushes the CPU hard can easily push the temperature up significantly, as the CPU's boost algorithm kicks in and pushes the clock to the limit.
As it happens, I have a single runaway thread hammering my 5950X as I write this, so I've currently got a 65C CPU temperature and 75C CPU package temperature with a 360 AIO from a CPU that will usually idle in the 40s. The 7950X(3D) is even hotter than the 5950X.
As for finding what's generating CPU load, there many tools around to help you look at what's going on. For basic MS tools, there's Task Manager and Resource Monitor. For a much more advanced tool, there's Sysinternals Process Explorer. N.B. a single thread running at 100% on a 32 thread CPU (like your 7950X3D) shows up as 3.125% CPU usage. It's perfectly normal for there to be some constant light load that adds up to 2 or 3% on a mostly idle system, and the CPU % numbers don't entirely tell you if the usage is heavy or light (some computation is more complex and harder for the CPU to process than other stuff) so don't assume that everything that's using a little CPU is a problem.