I dont see how this is possible with cable steering unless something is terribly wrong!!! Full hydraulic will do that when it is not completely bled properly. If it is a rack cable I would seriously look at everything in the helm to be sure it is tight. Also, check the large nut at the end of the cable housing at the transom. It secures the cable to the steering tube on the transom assy. If it is loose you will be able to grab the cable and move it back and forth. This will cause your problem. The cable should not move back there. I am talking about the cable housing, grab it just before the nut and try to move it. Attempt to tighten the nut even if the cable cant be moved.