Our Cavalier King Charles Spaniel Is 4 Years Old. She Has Not Slept All Day For More Than 5 Minutes When She Wakes Up Crying. This Has Never Happened. All Other Signs Are Normal. Do We Need To Be Concerned?

I would guess that she's gotten into some kind of pharmaceuticals (uppers of some sort)... But you didn't mention that she is acting in anyway unusual when she's awake.. Which doesn't seem consistent??? 
Is she acting any more anxious or hyper... Eyes moving a lot.. Jumpy... That sort of thing when she's awake?.. If so then I stick to my original diagnosis.  If you have a child in the house who takes ADD meds, it's not unusual for a pill to drop unnoticed at some point, and eventually the pup finds it and takes a trip... Or are there any plants she's been chewing on, or anything unusual going on around the house... Painting.. Glueing.. Fertilizing.. Spraying for pests..??  If it's not a med or toxin.. Then I'm stumped at this point.  
I'll do some reading up.. to see if I can come up with something else... But that's all that comes to mind right now.