I am having errors pop up quickly (can't read them) before my login window appears. I can't find them in syslog. Is there some way I can figure out what these errors are?
journalctl -b "should do the trick" ... this will show the journal entries that have been collected since the most recent reboot.
journalctl -b -1 shows the entries from the boot event before. Reference (and information) : How To Use Journalctl to View and Manipulate Systemd Logs
To see additional options you have with
journalctl, such like
journalctl -b --list-boots,
you can check them out by executing the commands
journalctl --help or