Open the Limit Reasons window when your CPU is stuck at its minimum speed. Is BD PROCHOT glowing red in Limit Reasons? This is the most common reason for this problem.
A wide variety of MSI motherboards manufactured during the last 10+ years have had this problem. With older motherboards, it was simple to use ThrottleStop to disable BD PROCHOT on the main screen. Starting with 12th Gen, most motherboards are now locking out the BD PROCHOT setting. If this setting is grayed out in ThrottleStop, it has been locked by the BIOS and cannot be adjusted.
If this is the problem, the only solution is to replace the motherboard. If you get another MSI motherboard, this problem might happen again at any time.
This is a hardware issue. The recent Windows update was likely a coincidence. When a sensor starts shorting out, there might be times where this throttling issue happens intermittently. Post some ThrottleStop screenshots if you need help understanding this problem.