Disable auto shutdown in computer monitors in lenovo

Your monitor may have an option to set it as "manual" or "auto". If set in manual, you will have to turn off the monitor power switch each time. If it has the "auto" setting , it should shut off or "go to sleep" when it detects no input signal.

The problem is probably at your TFT/LCD panel. Find to know by connecting your Notebook to another monitor is it dimming or not

The graphics card can only support two monitors at a time. One being the notebooks built-in display and the other being either the HDMI or VGA ports. You will have to attempt to disable the notebooks built-in display. Good luck.

Restart the Computer and keep tapping the F8 key till you see the advance boot options, You should be tapping the key as soon as you see the manufactures screen. Once you get the advance boot options -> Select the option which says Disable Automatic Startup on System Failure.
Good Luck!!!

try by power reboot

Try to hold down shift several times and reboot your computer. As soon as you see the lenovo sign shift again till you get to safe mode.. This might allow the monitor to stay on to trouble shoot ...If not you will have to call lenovo.

Im not aware of any such shortcut keys to disable a monitor. If your using a laptop then its FN+ One of the F1 to F12 keys.

When systems power off suddenly, always suspect - the power first. I would then look at heat and physical connections next as culprits. Memory errors almost always show up as blue screens.
I say try a new power supply and see what it does. Its not a lot of money either way.

Run CPUID Hardware Monitor and watch your temps. You will have to turn logging on or you will lose the data in a crash.
Make sure your CPU heatsink is still connected properly. Things have a way of working loose.

go to system properties & disabled system auto restart

Go to Start > Run and type services.msc. Locate the nVidia Driver Helper item and right click it. Select Properties. Set the startup value of the service to “Manual” or “Disabled”.