It could be that your top nut on your rudder stock is slightly too tight? But be careful, I would expect it to be too loose rather than too tight. If it’s occured for no reason and you have not alterd anything then maybe something is rubbing the steering cables, worse still like mine I had a wire caught in one of the steering pulleys!

    Remove the panel from the aft cabin and put your head in to the lazerette, look port side into the area under the binnacle and check for anyting amiss. While your there check your rudder stock where it runs through the cockpit sole down through the hull inside the lazerette.