Last Firday or Saturday my iMac (OS High Sierra Ver 10.13.6) turned Screen Black automatically. For next two three days, it would not boot up, screen turned black again. Would quit before the main screen. Then today it boot up, however were slow. So far no problem for six hours. Question is why?
Was there any security update that required restarting a few times? Or it needed so much time to update because file was large.
Thanks,
Satish
iMac, macOS 10.13
Satish,
Your description sounds like a hardware failure however you can try some basics such as attempting to boot up in Safe Mode (note this can take up to 10 minutes so please be patient). When you say "Would quit before the main screen." you need to be more descriptive and tell us exactly what you see and hear. Remember without those details we can only guess what you mean.
If I am correct and it is hardware a forum cannot diagnose or help you find what failed. Your best option in that case is to take the computer to your local Apple Authorized Service Provider and have it professionally diagnosed and serviced. If you don't know of any in your area please click Apple Authorized Service Provider Locator (AASP) & Genius Appointment
startup issue
