My iMac goes into a boot loop when I switch on: logo and most of black line appear, black line completes, blank screen, then machine shuts down, then restarts automatically and so on. (I have reinstalled software as per Help onlin.)
iMac 27", macOS 10.13
iMac 27 refuses to boot. When I switch it on, logo and most of black line appear. The line completes and blank screen appears followed by auto switch off, then auto reboot, at infinitum. (I have reinstalled software. Makes no difference.)
Sounds like Video Card perhaps...
Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?
Did you make any headway on this?
My iMac goes into boot loop when I switch it on: Apple logo appears with five sixths of black line, the line fins
