Log in Web site

Go step by step and test.

1. Launch Safari holding the Shift key down. 

    Test.

2. Startup in Safe Mode   https://support.apple.com/lv-lv/HT201262

    Login to your account.

    Lauch Safari.

    Test.

    To exit Safe Mode, click the  in the menu bar and then “Restart”.

3. If Safari doesn’t load website pages

    https://support.apple.com/guide/safari/if-you-cant-open-a-website-ibrw1071/mac

4 Safari > Preferences > General > New window opens with:

Make sure "Empty Page" is not selected.

5. In some cases this can happen if adware, anti-virus software or cleaner type application are installed.

    To find out, run EtreCheck and post the report here.

      https://etrecheck.com

      Click  “Free download” button,

      Open Downloads folder, click on it to open, and then select ”Open”.

      “Choose a problem” from the popup menu box, and then “Start EtreCheck” in the dialog.

      Click “Share Report” button in the toolbar, select “Copy report” .

      Paste the report when you reply.

EtreCheck report is not complete.

Try removing website data for that particular site.

Cookies store login information.

https://support.apple.com/guide/safari/manage-cookies-and-website-data-sfri11471/mac

Please post the report in Pastebin so it is readable. hthttps://pastebin.com/

Are you running any anti - virus programs? Using a VPN?

Try setting up another admin user account in System Preferences/Users & Groups to see if the same problem continues.

Isolating an issue by using another user account https://support.apple.com/en-us/HT204443

Try running Etrecheck again and post the report in Pastebin. https://pastebin.com/