The first typed characters of my query are missing

If you find that when pressing Cmd + Space, the first characters you type are missing from your query or the Alfred window doesn't appear the first time, there is most likely interference with the hotkey.

If you're on macOS 10.13 or more recent, take a look at your System Preferences > Siri, and change the "Hold Command Space" shortcut to a different one, in case your Mac thinks you're calling up Siri.

Alternatively, you can disable the Siri feature altogether if you don't use it.

You may also need to follow these steps to check Cmd + Space isn't in use by Spotlight, for language switching or by a third-party application.