Good to hear. It was probably the power surge at startup (drive spinup, CPU and GPU init, etc) overloading either the PSU proper or one of the rails. Why the system drew less of a power spike when warm might have been due to it still having some charge left in its capacitors rather than actual heat. Or maybe it just changed the electrical properties of whatever was failing in the PSU. Who knows or cares, it's just good it's fixed.