Either an OS or an app update could cause this (though I can't rule out more esoteric possibilities). Did the problems all start at the same time, and had there been either OS or app updates shortly before it started? If many started at once that would obviously suggest a common cause (I've known app updates introduce very similar problems, but never many of them at the same time). If you haven't had an OS update recently I wonder whether something like Play Services, which has its sticky little fingers everywhere and updates silently in the background, might be a possible cause?
You could try clearing the cache of one of the worst affected apps and see whether that helps. Or reinstall it (might help if an OS update were behind it). Or maybe clear Play Services' cache, just in case (that's the one possible common factor other than the OS that occurs to me).