It sounds like there might be a loose power connection. Possibly in the power cable itself or where it plugs in on the computer. You might also want to check the battery, make sure the connections aren’t dirty or loose or any other possible problems. You might want to check the power cable “Box” thing. If you’re tilting the computer, does it tug on the power cord? You might try tugging on near the box to see if the computer shows the power cable light. Since this has to be a hardware issue, you might want to take it in to wherever you got it, or somewhere to have it looked at.