Abort a shutdown by Software Center 

Refer to this blog post https://www.rlvision.com/blog/stopping-software-center-from-restarting-your-computer/ 

Using command prompt – shutdown /a 

This will suppress the reboot, but the prompt will remain active.

Try PowerShell –  

do{shutdown /a ; stop-service ccmexec ; sleep 1} while (1 -eq 1) 

To stop/suppress the Software Centre prompt – kill the process in task manager "SYNCHRONIZATION --> CCM"