Hello Neil, welcome to the Microsoft community, I'll be happy to help you today;
I understand that you are having issues with shutdown and startup in Windows 10;
Initially I recommend that you check if you are updated with the latest version of Windows 10;
Press Windows key + i and go to Update and Security;
Click Check for updates and do ALL pending updates;
Disable apps running in the background;
Press Windows key + i and go to Privacy;
Click on Background apps and turn off the option;
run a disk cleanup;
Press Windows key + R and type: cleanmgr press Enter;
Click on clean system files and wait for the files to load;
Select all files and click ok to delete them;
Perform a clean boot;
Press together the keys: Ctrl + Shift + Esc to access the task manager;
Click on start and disable all programs that start with Windows;
Restart the PC and check if the behavior still persists;
See you soon!