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You may have an issue, that when the computer is "cold", you have the error, and as it "warms up", the hardware error isn't present. This could be that the power supply isn't delivering the proper voltage/wattage cold, or it could be components. The first thing I would try is a power supply replacement.....it is the easiest to determine if it is the problem.

You can also unplug all devices except the mobo and GPU (if applicable), and try a cold boot. It may be the mobo/gpu in the computer - replacing the mobo is the most difficult thing to do....and you might have to replace the CPU as well....