Are they horizontal lines? And they don’t show up in the photos (once you export to a computer)? It’s completely a guess, but I’d assume that the electrical contacts for those lines have become detached/corroded/broke. So long as it doesn’t affect your final photo I’d say just live with it. Fixing a camera that old isn’t worth it, so live with it or upgrade are your options.
If they do show up in the final photos then I’d guess that your sensor is damaged. There are no settings that would do that, so something is damaged. Again, with a camera that old it wouldn’t be financially sound to repair it, whatever it is.
