Looks like a transient hardware issue. Those are difficult to diagnose. Only find a repair shop if you can consistently reproduce it.
As of yesterday, 10/15, my Toshiba Satellite M305-S4910 screen started flickering now and then and at one point, it went black. So I shut it down and restarted it. It seemed to help and didn't do it again the rest of the day but I'm worried that something serious is wrong. Any ideas why it'd start to do this out of the blue?