Go step by step and test.
1. Update Safari, if an update is available. Update may come with bug fixes.
https://support.apple.com/en-us/HT204416
2. Quit Safari, launch Safari holding the Shift key down.
https://support.apple.com/en-us/HT203987
3. Startup in Safe Mode. https://support.apple.com/guide/mac-help/start-up-your-mac-in-safe-mode-mh21245/mac.
Login to your account in Safe Mode test.
Quote:
It also does a basic check of your startup disk, similar to using First Aid in Disk Utility.
And it deletes some system caches, including font caches and
the kernel cache, which are automatically created again as needed.
4. If Safari doesn't open a webpage or isn’t working as expected
https://support.apple.com/en-us/HT204098