Blank screen after ACPI turn it off or suspend

Hello everybody,
I use OpenSUSE Leap 42,3 on a Dell Inspirion 1525 (Intel i915 graphic chipset).

It seems ACPI cannot bring my monitor back on after I suspend it or turn it off due to inactivity. I am using it as root and I use KDE.

It is rather annoying because I have to reboot the machine to bring the monitor on (I switch to screen 1 by ALT+F1, login as root and reboot, all blindly).

Can you please give me some advice?

Thank you very much

Never run a GUI as root!!!

Sure thing you will break stuff.