That sounds like a graphics related problem rather than one in which the screen is going to sleep, but it could also be other things. It appears your machine is still under warranty. But before taking it to Apple to look at, try hooking up an external monitor or even a TV to your MBP. Let's see if it does the same thing.
Something else to try.... Boot up in Safe Mode. Hold down the shift key as soon as your hear the Bong sound. If the screen stays on OK in safe mode the problem could be caused by software in normal mode.
Also check to see that you don't have "Hot Corners" turned on. System Preferences, Desktop & Screen Saver, Screen Saver Tab. If you have a hot corner setup to sleep the display, whenever your mouse or trackpad hits that corner, the display will black out. You be surprised how many folks unknowingly have hot corners on.