My late 2015 iMac has suddenly been powering off at random times. I mostly find out its off in the mornings. I am unable to power it back on by pushing the button and the only thing that allows me to power it back on is if I remove the plug from the back of my iMac, wait for about 30 seconds, then plug it back in. My iMac will then boot up. I tried resetting SMC and PRAM. Question is, is their any logs that could help me determine what is happening? Maybe I have a bad power supply?