Keychain Access.app freezes

Boot into Recovery (Command R) and from the dropdown menu: Utilities>  Disk Utility> run the First Aid on your Macintosh HD (and the "Macintosh HD-Data" volume as well if Catalina) If errors are found and repaired, run again until no errors reported.

Recovery: https://support.apple.com/en-us/HT204904

To trouble shoot further you can:

Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc. Login and test. Reboot and test

If no difference or change, you can reinstall the macOS from Revovery on top of your existing macOS to sort anomalies.

You do not say what exact Mac /model /year /size /retina /touchbar is this 

or

what exact macOS you are currently running? 

And how did First Aid go from Recovery?

To get a good look at your System config. for conflicts or issues, you can run this trusted utility http://etrecheck.com  

If you need help interpreting the report you can post it here in its entirety in the "Additional Text" box in the editing toolbar below, in your reply.

You can set its preference to "Allow full Disk Access",  with this you get a digest of issues from the last 7 days that are saved in your system.