36" RCA tv scans channels on its own and won't stop?

I have a 36" RCA standard tv model F36668 bought new Oct 2000. You can be watching tv then channels start scanning. Goes from 70 to 99 then to VID then to channel 1 then to 3 then to 70 and starts over. It won't stop scanning those channels. This has happened a year or so ago and unplugging it is what stopped it then. Thats not working this time. If you push any button on remote it speeds up. I use cable box so ch 3 and VID are only ones programmed on tv.