I restarted Fedora (32) after an upgrade having not restarted for around a week. After putting in password it hangs at a grey screen. I tried booting earlier kernel but no difference. I can boot if I choose gnome-classic though. I looked in logs for previous boot and can see some errors:
I would start with logging in a text console, e.g. Ctrl + Alt + F2 and then running.
mkdir -p "$HOME/save" mv "$HOME/.local/share/gnome-shell/extensions" "$HOME/save"
This will remove all installed Gnome extensions. I've noticed some errors related to them. Try logging in after that.
In case it doesn't help again go to a text console (make sure you're not logged on) and run:
mkdir -p "$HOME/save" mv "$HOME/.local" "$HOME/.config" "$HOME/save"
This will remove all your settings but will most likely fix the issue that you're having.