iMac 16,1
21.5in, late 2015
Core i5
OS X El Capitan 10.11.16
(I am an Apple novice)
Boots up OK, then after about five minutes the display jerks left and right a couple of times. This increases gradually until it goes crazy for about 20 secs when the computer shuts down and reboots. If left to itself it will repeat this performance ad infinitum.
By chance, on one occasion before the screen started acting up, I initiated a McAfee full scan. The display fault did not occur, and as the scan takes hours, I was able to use the computer as normal. This has been tested multiple times, and as long as a scan is in progress there is no display problem. Any ideas ?
Zen.
Three pics attached.
21.5in, late 2015
Core i5
OS X El Capitan 10.11.16
(I am an Apple novice)
Boots up OK, then after about five minutes the display jerks left and right a couple of times. This increases gradually until it goes crazy for about 20 secs when the computer shuts down and reboots. If left to itself it will repeat this performance ad infinitum.
By chance, on one occasion before the screen started acting up, I initiated a McAfee full scan. The display fault did not occur, and as the scan takes hours, I was able to use the computer as normal. This has been tested multiple times, and as long as a scan is in progress there is no display problem. Any ideas ?
Zen.
Three pics attached.
