In case windows 10 (64bit pro in my case) has been updating itself, IMO the cause of many problems, switch it off PERMANENTLY with a tool called windows 10 update switch. Windows update should be only allowed to run on special occasions f.i. with security updates. Roll back your graphics drivers, or maybe install the latest ones, and read this: stuttering
Switch off hardware acceleration manually in device manager if you can find, for your GUI driver's settings.
More: fast startup and as Matt said, there are more possible causes like processor behavior slowing down due power or hibernation settings usually not necessary on a desktop anyway.

If Windows 10 pro is tuned right it's a great OS, but Microsoft lets it's more professional users really down by forcing us to use it with far too many unneeded gimmicks and useless bollox. Worst is that when you leave Windows updates active, or even off in services, it resets it self on again. And all of those carefully turned off settings too. I am in the process of installing W10 LTSB enterprise, supposedly better at that. -F