A similar thing has been happening to a website I am working on. The server started crashing on a regular basis, and then the whole wordpress admin panel started taking a very long time to do anything. It would open to the dashboard if you waited a minute or so, and then would take long enough I gave up waiting to access anything else (several minutes).
Everything online said to deactivate all your plugins and reactivate one a t a time to see if that is the problem. Brightcove is where it slowed down every time. I have left it deactivated now, but I still need to play videos from Brightcove. Help!