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.
On your Mac, you can also update your settings to prevent windows from opening again
after you close Safari, or just press and hold the Shift key when you open Safari.
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.
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. Clear History
https://support.apple.com/guide/safari/clear-your-browsing-history-sfri47acf5d6/mac
Please read the article before clearing history,
this is like a low level resetting of Safari without affecting passwords and bookmarks.
5. If Safari doesn't open a webpage or isn’t working as expected
https://support.apple.com/en-us/HT204098