You can check the power settings for the display in "Control Panel" and make sure they are set correctly.
1. Go into "Control Panel" and then "Power Options".
2. Click the "Change plan settings" link next to which ever plan you are currently using and then click "Change advance power settings".
3. In this new window click "Display" to open up the listings under it.
4. Change each of these to the settings you wish, then click the "Apply" button and finally the "OK" button.
5. Reboot and see if the problem is gone.
Should you still have problems at this point, then I would start to wonder if the battery is going bad. If it isn't putting out enough power needed for the device to run properly, including the display, then a battery...