Are you presented with a Grub menu when BIOS POST completes? If so, strike the
E key. That allows you to append a
3 to the line that begins with
linu. That should allow you to reach a login prompt. From that point, more diagnostic information can be acquired if needed. Fixing may be as simple as finding and changing the configuration file for the login manager. Likely that filename is
/etc/gdm/gdm.conf. If so, change AutomaticLoginEnable=
true to AutomaticLoginEnable=
false. To make that edit requires superuser permission. If mc is installed, you can use it to both locate that file, and edit it.
Code:
sudo apt install mc
if it is not installed.
