A couple days ago while I was using my 15 inch Macbook Pro 2015 Retina Display laptop (got it brand new 2-3 months ago, running latest version of Sierra), the screen flashed black a few times, and then completely went to sleep on its own while I was in the middle of something. I couldn't get it to wake up, so I had to force restart it. After that, I couldn't get it to turn back on unless it was connected to a power source. As soon as I would turn it back on and login, the screen would go black again. Even just opening finder or safari or sitting on the desktop would make it go black.
I looked online and attempted resetting the SMC and PRAM several, several, several times. Sometimes, I would login and the screen would be completely distorted and discolored. I attempted logging in via the Guest account, and browsed Safari for 2+ hours just fine, but as soon as I went back to my user account the problem started again. I rebooted and ran the disk utilities and even re-installed Mac OS completely. I still have no luck, and now, sometimes when I turn it on, the "startup chime" will play over and over again every 2 seconds like it's trying to start up but can't.
I'm not sure what to do at this point as I've already tried a fresh install of Mac OS. Next, I was thinking of erasing my drives but before I do that I want to see if there's anything else I can do. I even changed all of my system settings to not dim the screen display and to never go to sleep because the screen was randomly dimming at times.
P.S. I'm currently typing this on the Macbook after booting it with command+r and clicking on "safari help", again it works fine in when logged in as Guest too, it's only after I login to my user account that this happens. Sometimes it's immediate, sometimes it takes a few minutes.