Might be an incompatible Safari extension or plug-in causing the freeze ...
Try troubleshooting extensions and third party plug-ins.
From your Safari menu bar click Safari > Preferences then select the Extensions tab. Turn that off if there are any installed. Quit and relaunch Safari to test. If that helped, turn extensions back on then uninstall one a time to test.
If it's not an extensions issue, try troubleshooting third party plug-ins.
Back to Safari > Preferences. This time select the Security tab. Deselect: Allow all other plug-ins. Quit and relaunch Safari to test.
If that made a difference, instructions for troubleshooting plugins here.
I have recently had the same issue, Safari would beach ball when the share button was pressed.
After following your suggestions I was unable to resolve the issue. My next step (because there was an update recently and the issue appeared to rear it's head after applying the update) was a total removal of Flash (not just the plugin). In my case this seems to have resolved the issue, I will leave Flash off and if I REALLY need it I will just use Chrome).