MY MONITOR KEEPS TURNING OFF! MAKE IT STOP AND HELP FIX! :((?

so I had a monitor and one day it kept turning off each while but not every second or minute! when i move my mouse it does not turn on! so i had to keep restarting to make it turn on and fix it and go back to what i was doing. when i restart my computer I open up my computer and hold the button until the computer turns off and i press the button to turn it on and the monitor turns on! one day when i was restarting to fix i had to get a new hard drive and it had a black screen and said something about BIOS. so i got a new hard drive and a new monitor. And then it still keeps turning off! and when i move my mouse it still does not turn on! and when i press the blue glowing button it says no signal or something. i doubt its a bad unwanted program! please tell me what is wrong with my computer or monitor!