My HP's screen goes black

When your computer reboots, go to the control panel > power options > go to the hibernate tab and turn off hibernation. Then go to the power settings and make sure to change the setting for closing the lid to "do nothing" then change the other settings such as when the computer sleeps if inactive to 30 minutes to an hour. Hibernation is causing the most problems I see with random shutdown etc. One other thing it might be also is overheating of the processor, make sure to get some compressed air and blow out the heatsink vents and grills on the base of the laptop. If these are insuccessful, there maybe the possibility that you have a Malware bug. Go here http://www.filehippo.com/download_malwarebytes_anti_malware/

download and run this and perfrom a quick scan, when it is finished, show results and delete anything it finds.