Temporarily disable anti virus software if installed.
And try resetting Safari. From your Safari menu bar click Safari > Reset Safari
Select: Clear History (also empties the cache)
Deselect the remaining boxes then click Reset.
Quit and relaunch Safari to test.
If that doesn't help, back to the menu bar, click Safari > Preferences then select the Extensions tab.
If there are any installed, turn that OFF, quit and relaunch Safari to test.
If that doensn't help, back to the Preferences pane, select the Security tab.
Deselect: Enable plug ins
Quit and relaunch Safari to test. If that made a difference, follow the instructions for troubleshooting Safari add ons here.