Sometimes it can be Windows itself if the minimum/maximum % of CPU isnt both set to 100% (done in Energy Options).
Had that once on a PC where he used only half of the Processors and those he didnt use was at 0%.
For a Laptop i can see Power saving reasons there, have u checked the Power settings for windows, if u have connected the Laptop to Power Source try to run it at the maximum Power/Efficiency setting. But be sure to monitor temp when u do that.
Also Windows 10 by default does not really do a "shutdown", it goes just to a deep hibernate mode, so u need either to do a restart to have a fresh clean system or have to deactivate the fast boot in Energy Options, by deactivating Win10 does the shutdown we are used from previous Windows OS.
Greetings