Spotlight on Mac doesn't accept keyboard input

Periodically, Spotlight stops responding to keyboard input on my Mac. When this happens, pressing cmd-space brings up the Spotlight search field, but typing search terms has no effect. Characters don't appear in the search field, and even pressing ESC doesn't exit from Spotlight. The keyboard continues to work normally in every other app-- only Spotlight is affected.

Rebooting restores normal operation but I'm hoping there's some non-reboot way to get things working again.

I'm running macOS 10.12.5 (16F73) on a 15" touch bar MacBook Pro. Both the internal keyboard and an external Apple USB keyboard are affected.

This seems to have worked. I'd still be interested in other answers people might have, in case there's something better.

1. Run Activity Monitor
2. Type "spotlight" in the search field.
3. Several items will be remain. Select the one just named "Spotlight". Use the "x" button at the upper left corner of the window to kill it.

Spotlight automatically re-launches, and now works.

A more faster way than the GUI is through Terminal:

1. Run Terminal (via Application panel -> Other -> Terminal)
2. Type: killall Spotlight

Spotlight will restart and be operational.

If the above mentioned are not working then give a try for this:

1. Open Terminal

2. Type - not copy! - the following but wait a few second between them:

   sudo mdutil -i off /
   sudo mdutil -i on /
   sudo mdutil -E /
   

If, after a few minutes, Spotlight is still not indexing, try running this command, followed by the three commands above:

sudo rm -rf /.Spotlight-V100

This is the site where the help comes from, big thanks for it!:

https://www.amsys.co.uk/blog/how-to-fix-spotlight-search-on-a-mac/

h/t to https://all-about-apple.com/unable-type-spotlight-search-bar

Bring up spotlight via the system menu, press backspace. You might need to do this twice. No idea why this works...