Try troubleshooting extensions and third party plugins.
From the Safari menu bar click Safari > Preferences then select the Extensions tab. Turn that OFF, quit and relaunch Safari to test. If that helped, turn one extension on then quit and relaunch Safari to test until you find the incompatible extension then click uninstall.
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.
Thanks. I'm using Chrome instead. When Apple gets this fixed I might go back to Safari.
Anyway, I tried your suggestions, and it's the Plugins. But turn them off means I can't even open a PDF in Safari. However, it seems that I have to go all the way; when I turned the them off then on again, the problem goes away, at least for now.
Carolyn, what incompatible plugins? I only have what I got from Apple or Adobe CC. And As I mentioned, the problem disappears when using browsers other than Safari. So, I'd say Apple IS responsible, since Safari is their product. Wouldn't you?
As for Linc's comment, I think you should actually do a bit of research before making your statement. There are a loooot of people having this problem. And no one has found a solution, including Apple. I chatted with one of the their technical support and I only got the standard resetting the PRAM, …. This is why I posted my orginal comment, in case some might find it helpful.
Have a nice day everyone.
Carolyn, if there really were certain "icompatible plugins", then using Lync's logic, everyone would be having issues with the same few guilty plugins. So, if this is even a little true, then why can't Apple publish a list of "imcompatible plugins", based upon the number of complaints, or their own testing? This would save thousands of users unneeded aggravation, frustration and many, many wasted hours of manual, one by one, individual testing.
I'm beginning to think that "incompatible plugins" has become just another "let's do a clean re-install" as the go-to remedies/excuses for any issues we may have with Safari.