If your Windows 10 PC is taking an unusually long time to shut down, check to see if you have a USB Type-C device plugged into it. That could be your culprit, depending on which version of Windows 10 you are running.
"A bug in the USB Type-C Connector System Software Interface (UCSI) software implementation in Windows 10, version 1809 can cause a 60 second delay in the system sleep or shutdown process if the power-down happens while the UCSI software is busy handling a new connect or disconnect event on a USB Type-C port," Microsoft explains.
Version 1809 is what you're running if you installed the October 2018 update, but have not yet applied the more recent May 2019 update (version 1903). If you are unsure which version you have, hit the Windows key + R and type winver in the run command box that appears. Here's what you should see:
While the minute-long delay is annoying, especially if you are in a hurry, the bug does not affect the USB-C device in any other way—it should still work normally in your PC.
It's not clear if a fix is inbound for build 1809. However, Microsoft did say that it addressed the issue in build 1903. Microsoft initially staggered the roll out of the May 2019 update, so you may not have it, even if you have not intervened with the update process.
If not, you can head to Settings > Update & Security > Windows Update and select Check for updates to see if Windows will grab it for you. Alternatively, you can manually force the issue by following this link and clicking the Update now button. Just be sure to back up any important data first, just in case things go awry.