I have a late '15 27 inch iMac, 512 SSD, 3.3 i5, M395. On 2 occassions, the computer has restarted itself spontaneously. Because it has pure SSD, the restarts have been near instant. The first time was soon after opening it and booting it up the first time after restoring from time machine. As soon as I logged into OS X, the computer did a force restart and bounced me back to the desktop. The 2nd time was about a week ago, I have had the computer for about 5 months now, but I had a download going and I was playing a game (Elder scrolls online). I played for about 5 hours and after quitting the game, the computer did a force restart again and put me back to the desktop. Both times, no error message was displayed. I am very concerned if my computer is defective or if there is something triggering it. Can somebody please advise on the seriousness of this issue, and if there is a way to fix it? Thank you!