My dell optiplex 9020 started flashing the orange light twice.
The pc starts ok but after a few minutes you hear a click noise and then goes off. It tries to turn on a few times but fails and then starts flashing the orange light twice. 
I changed the cmos battery. I managed to do a diagnostic test f5 and found nothing wrong. I also clean and replaced the thermal paste of the processor but still the same.I  checked the ram, replaced them or moved them. 
If you leave for a few hours and start it it will boot and no problem but after a few minutes or may be half an hour it will do it again.