The phenomenon that affects folks (usually those who were born prior to 1950) at Starbucks, when they suddenly freeze and have no idea what to say or do when the barista asks them for their order when trying to buy a plain old cup of coffee.
Usually followed by groans and exchanged glances among the snotty cardigan-wearing yuppies and corporate scumbags in three-piece suits waiting in line behind them.
Can also be associated with the shock of paying more than $0.50 for a cup of coffee.
Customer 1: "Dude! Did you see that geezer get the Starbucks Stutter when he couldn't even order his joe?"
Customer 2: "Yeah! That was some serious java stage fright!"