Practically always, when you get problems, the first thing is to run a thorough scan with your antivirus, and also with, say, Malwarebytes, perhaps a check with CCleaner.
I don't know Norton, nor what your firewall is, but you can turn them on through Settings - you don't have had your license expired, by accident? Also, you shouldn't have several security programs running at the same time, in case your Norton includes one, like firewall, the other(s) may cause a conflict.
Pressing Ctrl+Alt+Del at the same time, go to Start Task Manager, there you can see what's eating CPU. It may be something you've installed lately?
By the way, I've had somewhat same kinds of problems lately, programs won't start with one click in the Start Menu, they require two clicks, sometimes a program won't work even if it started, I have to shut it down, after restarting it, it works fine. Could be a glitch, that will be in order after some Microsoft update.