What is wrong with my Sunbeam Radiant Toastermatic AT40?

When I turn power on (without bread in it ,and control on lightest) mechanism automatically goes down and elements come on. Only when I turn power off at wall does mechanism return to start. Therefore I am still able to make toast manually by turning on at wall, dropping bread in, watching toast colour up and then turning off at wall again! Can anyone give me some clues as how to fix please. Thanks Sheryl.