Last week my laptop has been updated to Windows 10 May update. It's an update I was waiting for, because I wanted to use the new WSL 2 features when using docker. So after the update I immediately activated WSL 2 using the command

wsl --set-default-version 2

After booting and signing-in it always take a little time to startup, so the first time I did not notice any real problems. But the days after that every time I started the laptop and signed-in I just got a black wallpaper without startmenu or taskbar. When waiting for a long time (approximately 2 or 3 minutes) suddenly the startmenu and taskbar did appear.

First I thought it was the WSL 2 feature, so I disabled that again, but that did not make any difference.

After searching on the internet I found this website: https://appuals.com/file-explorer-not-loading-or-loading-slowly-after-windows-10-upgrade/ 

On the website Solution 1 is to disable the Windows Search and that was for me the correct solution. After disabling the Windows Server service signing-in was fixed. Personally I did not find any other problems with disabling this feature.