My iMac will not properly start-up. It will cycle through the start up sequence for hours, and when it finally reaches the end, it will turn off and turn back on and start back from square one. Sometimes a power logo with an error message will come up and then do the same thing over again.
iMac 27", OS X 10.11
PRAM reset, CMD+Option+p+r...
http://support.apple.com/kb/HT1379
In fact, do 3 in a row, takes a bit of time.
Intel-based Macs: Resetting the System Management Controller (SMC)...
http://support.apple.com/kb/HT3964
Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?
How to reset NVRAM on your Mac
Use safe mode to isolate issues with your Mac - Apple Support
If it is failed hardware, then locate an independent Apple Authorized Service Provider in your area and take it to them.
How's it going?
Sounds like failed hardware, please attempt to reset the NVRAM and to start in Safe mode..
How exactly do I do that?
Because I don’t want to go into the hardware and start taking things apart.
iMac Start-Up Issues
