Computer screen sometimes won't start up again after sleep

Sometimes, after I close the lid or let it go to sleep, when I try to start it back up again, the screen doesn't turn on. The machine seems to be on, as I can hear the fans running and the keyboard lights are on, but the screen remains dark. I've tried pressing the power button, the Windows key, and even holding down the shift key while pressing the power button, but nothing seems to work. The only way I can get it to come back on is by unplugging the power cord and plugging it back in.

I need everyone's help ASAP. Thank you.