Comment # 1 on bug 911512 from Bernhard Wiedemann

please check or attach /var/log/Xorg.0.log

I think, the better command for starting X these days is
rcxdm restart


some other information might be helpful:
lspci -nn|grep VGA

and which driver do you use?

see also
https://en.opensuse.org/openSUSE:Bugreport_X