Hi, so I'm new here but I'm having a weird problem and I hope someone can help. My 1-year old iMac keeps shutting off with absolutely no warning whatsoever. Just straight-up hard shutdown at random intervals. This started happening after I tried (a few different ways) to stream videos, including: camtwist, livestream producer, and downloading the dmg for a red5 server (I wasn't able to make it work. I had no idea what I was doing. I just wanted to stream videos for my friends). After trying (and failing) to install the red5 server, the computer hard shutdown, and rebooted in Safe Mode, with the screen flickering white. I rebooted again, and it seemed fine. I deleted everything related to the red5 server because I thought "that was the last thing I tried, therefore it must be the cause," though I know that's not really rational. But that scared me, so I ran disk repair, and installed El Capitan, thinking... I don't know. I don't know! It seemed to work, anyway. For a like a week, no problems. Computer runs smoothly, no random shut-offs. ... Until today, when it did it again. For no reason I can discern. To rule out some environmental possibilities: it's a reasonable temperature where I am (70F~). I'm not running anything super intensive; all I had open at the time of the last shutdown was iTunes, Chrome, and Discord. My disk space is nowhere near full, and I have 16GB of RAM which should be sufficient for running 3 programs at once. I bought it in 2015 from Apple, not a third-party retailer, though it was refurbished (again, by Apple). Does anyone have any suggestions as to what I did wrong? What I could do to fix this? What this might be? Is it worth it to backup my data and do a clean reinstall of the OS? I feel like I screwed something up with the streaming programs I tried to download, but I'm at a complete loss as to what I might have messed up, or how to fix it. Here are my specifications. Please let me know if you have any thoughts or if you need any other info.