Go step by step and test.
1. Click in the menu bar and choose “Force Quit”.
Select Safari and click “Force Quit at the bottom of the Force Quit window.
Hold the Shift key down and launch Safari.
2. Safari > Preferences > Search
Uncheck the box beside “Include search engine suggestions” under Search engine.
3. Disable Extensions and test.
Safari > Preferences > Extensions
Select and disable all extensions and test.
Enable Extensions one by one and test.
To uninstall any extension, select it and click the “Uninstall” button.