Do you have the manual for this machine? It sounds like the clutch is partly disengaged for bobbin winding.
Manual can be purchased here http://www.singerco.com/accessories/instruction-manuals
type in your model number and press 'search'.
Does the fly wheel have an inner knob ? if yes, then grip the outer wheel and turn the inner one away from you to lock. Or there may be a button or indent you push. If it is an indent, then push on the other side to reset it to normal stitching mode.
Sorry, as I can't see the manual for this actual model am flying blind but I do think it is something to do with bobbin winding. Is the bobbin spindle turning when you press the pedal too?