Epson Stylus Color 640 printing problem

Almost everytime after I print something and the job is done, the printer keeps printing jibberish forever. For instance right now, I've loaded the same ream of paper over and over and it won't stop printing. Sometimes its only a few letters and other times it's 1/2 a page of jibberish. There is no sign of any print jobs under the control panel either, so I don't know what else I can do. I always have to turn it off and then turn back on and it'll work for awhile, but resorts back to printing jibberish for no reason??