Go step by step and test.
1. Click in the menu bar and choose “Force Quit”.
In the window that opens up, select “Safari” and click “Force Quit”.
Relaunch Safari holding the shift key down.
2. Safari > Preference > Advanced
Checkmark the box beside "Show Develop menu in menu bar".
Develop menu will appear in the Safari menu bar.
Click “Develop” to show the dropdown.
Click "Empty Caches" from the dropdown and test.
Safari Develop menu https://support.apple.com/guide/safari/use-the-safari-develop-menu-sfri20948/mac
3. Disable all extensions and test.
Section: Manage extensions:
https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac
4. Websites Data
“Remove stored cookies and data: Click Manage Website Data,
select one or more websites, then click Remove or Remove All.”
https://support.apple.com/en-us/HT204098