First and foremost, consult your DVD player manual and make sure the disk you are trying to run is supported by the player. The troubleshooting page has a list of supported disks. If it is, check the condition of the disk. If it is dirty, you can try to gingerly wipe it off with a soft cloth and try again. If it is heavily scratched, you might need to replace the disk. Download the product manual for instructions on how to clean your disk. If your DVD disk is clean, serviceable, and supported, you may have to look at your optical drive.
Check your AV connectors and ensure they are plugged into the proper AV ports. If everything checks out with your AV cords and the problem still persists, take a look at your TV settings and make sure it is in the proper display mode.
Ensure that your power supply cord is plugged in. If you are using an extension cord, ensure that the extension cord is plugged in securely. If you are using a power strip, make sure that it is plugged in and that it is switched on. If the problem persists you might need to replace your power cable.