Notification Center acting buggy

This behavior started today. 1) Notification center stopped showing whether I used 2-finger swipe (which I keep turned on in system preference) or clicked date/time. Restarting my Mac would make it work again. 2) However, every time I click on something in Notification Center (whether a widget or notification stack), I get spinning pinwheel, even when I have plenty of available RAM. 3) The only way I've found to stop this is open CleanMyMac X where I see it as a hung application. If I quit Notification Center, it disappears, but then will not reappear, without a restart. Back to #1 above.

Ideas? I haven't downloaded anything before this stopped working. I use Notification Center dozens of times a day, so this is definitely new.