Janis I have had two vintage machines that seemed to want to sew by themselves. The kids thought they were ghost machines because the machines would just keep on sewing even when they took their foot off the pedal! Both of them were a very simple fix. DH took the foot pedal apart and said there was something in there stuck - a spring or something. I didn't fix them or I'd tell you exactly what he did, but this was a few years ago when I first got into the vintage machines. I remember, he just unstuck something and I have no problems with them since.
Nancy