To check the if there is a stored code. I believe you have to turn the ignition switch on for 2-3 seconds, off for two to three seconds, on for 2-3 . of course with the fuel pump switch on. there will be a series of 6 or maybe 8 flashe twice followed by slower flashes, they will have a slightly longer pause between the error numbers. usually a two digit code. example after the series of fast flashes, flash pause flash flash flash. This will represent a 1 4 code. If there is more codes stored there will be another series of 6-8 flashes ect, followed by the slower flashes.
I had this happen to me, and like you said it went away after just a few seconds. not to come back until after shutting down. Mine had stored codes, and it was + battery voltage, and crank/cam sensor. Never came back after I changed out the battery. But that was just my situation. At least you can check what is stored though. Scot