Hello there, this is Emily.
Just to clarify, this happened after install already gone through, and it was at the page where it counted down to restart, right?
If so, go ahead and remove the flash drive and see if Windows boots.
Otherwise, go to your BIOS boot menu/option and see if you have the Windows boot manager option? Set that as your boot priority and see if it works.
If neither works, can you tell me at what screen it restarts? Right after HP logo, or after Windows logo? Thanks!