My iMac has been shutting itself down for two nights now. I have to press the button at the back of the monitor to get the screen on. I did not shut it off in the first place. Today it started up the same way but had a degraded looking screen saver. I restarted it and all was normal. I then went to disc utility to run first aid just in case. For the first time the wheel (indicating loading) just kept spinning. The HDD never loaded on disc utility. So I turned it off and tried again after restart for a second time. Same thing. The iMac itself is fine; no problem. But the disc utility not loading anything puzzles me and I believe I need to address that problem ASAP. Problem is, I am not sure how to do so. Suggestions are needed and appreciated.