Even though I have Safari set to open with the tabs/windows I had open when I quit, it often starts up with a blank window.
With Safari open, press Command + Option + E to empty the cache.
Quit and relaunch Safari tot test.
IF that didn't help, open a Finder window. From the Finder menu bar click Go > Go to Folder
Type or copy paste the following:
Click Go then move the Cache.db file to the Trash.
Quit and relaunch Safari to test again.
Retrieving data ...