Microsoft explains why restarting Windows can shut it down more completely than shutting it down

Microsoft explained the difference between 'Shut down' and 'Restart' in Windows: with Fast Startup enabled, shutdown saves part of kernel and driver state to hiberfil.sys, while restart fully resets the session and boots from scratch. Thus restart is slower but more reliably resolves driver and service failures.

• Fast Startup is enabled by default and saves kernel state on shutdown
• Restart ends the kernel session and reloads all drivers
• Full shutdown without hybrid mode: command shutdown /s /t 0
• Microsoft does not recommend disabling Fast Startup