Why is my CPU spiking at idle, and how can I fix it?

I've been dealing with a frustrating problem on my relatively new PC that I built about four months ago. Lately, I've noticed that my CPU usage spikes randomly, even when I'm not running any heavy applications, and it's not showing up in Task Manager. The usage can jump unpredictably, and while the temperature of my CPU seems stable during these spikes, my system significantly slows down for durations ranging from 2 seconds to over 5 minutes. Luckily, my computer hasn't crashed or experienced a blue screen yet, but it's definitely impacting performance and usability. I'm running Windows 11 on a Ryzen 7 7800X3D with a B650 PG Lightning motherboard and an AMD Radeon RX 9070 XT graphics card, paired with 4TB of m.2 storage.

I've tried a bunch of troubleshooting methods like factory resetting the computer, reinstalling drivers, testing the CPU, storage, and RAM, and even running several antivirus scans to check for malware. I even had the CPU replaced at a repair shop. Some of these steps have temporarily alleviated the issue, but it always seems to return. Has anyone else encountered this problem? Any suggestions would be greatly appreciated!