Don't login to your shell as root, just as $user,
then it's the same:
startx
Ok I cannot launch X session from tty7, default console, as the normal
user. But if I change the allowed_users value in
/etc/X11/Xwrapper.config file from "console" to "anybody", I can
launch it from tty7.
From what I understand this is a security risk to have anybody launch
X, therefore left it as "console".
the only way I can launch a separate X session is to first log into
another console first and then launch X. This works without any issue.