Hi Scotty,
My niece has told me her 2008 Mazda 6 occasionally behaves in a way that when at a stop light the car wouldn't do anything when pressing the gas pedal unless she turns off the car and restarts it. A light comes on for a second but goes out. Could it be an issue with the electric throttle control?

yes, that or an electronic problem in the transmission control system. Find out which light comes on, there are various warning lights and a good mechanic can scan it and tell you what code exists