Go step by step and test.
1. Empty Caches
Safari > Preference > Advanced
Checkmark the box for "Show Develop menu in menu bar".
Develop menu will appear in the Safari menu bar.
Click Develop and select "Empty Caches" from the dropdown.
2. Safari > Preferences > Extensions
Turn off Extensions if any and launch Safari again to test.
Turn on those extensions one by one and test.
3. Delete com.apple.Safari.plist file and test.
Empty the Trash.
Quit all applications.
Hold the option key down and click the "Go" menu in the Finder menu bar.
Select "Library" from the drop down.
Library > Preferences > com.apple.Safari.plist
Right click on it and select "Move it to Trash".
Restart. Relaunch Safari.
If this doesn’t help, “Put Back” the com.apple.Safari.plist.
Right click on the Trash icon in the Dock and select “Open”.
Right click on the com.apple.Safari.plist and select “Put Back”.