In some contexts, retrieving keys on Windows 10 is extremely slow. I have a keyring with 34 keys. However, Kleopatra cannot load the keyring within many minutes. Also, LibreOffice is affected. See:
https://bugs.documentfoundation.org/show_bug.cgi?id=126172
In other context, i.e. Enigmail, retrieving keys works.
Unfortunately, so far, I only can vaguely describe the symptoms.
You probably have one of the spammed keys in your keyring. This is a problem with the keyserver networks. Do not use --auto-key-retrieve and avoid using the keyservers until we provide a mitigation with the next gpg4win/gnupg release. See also T4591
gpg4win 3.1.10 did not fix this issue for me, neither in Kleopatra nor in LibreOffice.
After waiting for far over an hour, Kleopatra read the keys. Now, things go faster (also in LibreOffice), but it still takes around 30 seconds, which is quite long.
If you're on a platform that has awk available (any GNU/Linux and macOS should provide it), you can scan for the largest OpenPGP certificate in your keyring with an awk script i posted over at https://dev.gnupg.org/T3972#127356
I'm not sure how to do it on windows though, sorry.
I think that even if the reason is corrupted keys it would be good to handle this better, either in Kleopatra or in GnuPG. e.g. Kleopatra could detect if a keylisting takes too long and offer to do some cleanup programatically.