LG monitor keeps switching to power saving mode.

So i was playing a survival game, graphics werent too big, just decent+ ? , and then suddenly my pc shuts down, and i try to open it agaim but it keeps saying "power saving mode" then switches off (red light) and i tried unplugging pc and monitor from eachother, i also switched on and off the pc alot of times, i cant see the screen and keyboard wont do anything, i have this for the third time but i fixed it by randomly clicking switch on/off and restart buttons, but now it doesnt work, is there a way to fix this without going inside my pc or monitor? How do i completly restart (without deleting anything) my pc using the switch on and restart button? (Restart button just switches off and on)