Hello vblasi,
Welcome to the HP Forums! I hope you enjoy your experience!
I understand the computer will shut down randomly. Usually this is hardware related, but I will do my best to assist you! To troubleshoot the issue, please try the steps in this HP document: The Computer Restarts Unexpectedly (Windows 8)
These troubleshooting steps need to be attempted to resolve the issue. If not, the computer should be serviced. Please contact HP phone support if you get to this step.
You can utilize this website to learn how to contact HP appropriately, based on your region: Contact HP Worldwide
Please let me know if you have any other questions or concerns. Thanks for choosing the HP Forums. Have a great day!
Mario