I am facing the exact same problem, as do many others judging by recent threads on the topic. By PRP_53's recommendation I did the EtreCheck to get a better insight and I suggest you do the same. Since this thread is about your system primarily, I will not share the entire report but highlight some initial findings.
1. There was no Antivirus software present.
2. Among recent installs were XProtectPayloads (125) on February 5th 2024, and XProtectPlistConfigData (2185) on February 12th 2024.
3. Besides familiar apps that have always functioned, and haven't updated for at least a year, there were two reports of high CPU usage that stood out. The latter may be related to Time Machine which I only activated two days ago, well after the issues began:
2024-02-17 15:37:01 ArchiveService - High CPU Use
First occurrence: 2024-02-17 15:42:58
Executable: /System/Library/Frameworks/FileProvider.framework/XPCServices/ArchiveService.xpc/Contents/MacOS/ArchiveService
2024-02-17 10:05:42 mdsync - High CPU Use (2 times)
First occurrence: 2024-02-16 13:26:37
Executable: /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/Metadata.framework/Versions/A/Support/mdsync