I would start with Davehrab's suggestion. Have you tried turning the unit off for ten minutes and then tryed loading a disc. If it plays and/or plays a portion of the disc then stops. I would say that it is probably the power supply for the transport or related components. If that doesn't reveal to be the problem then go after the dirty lens solutions suggested. You didn't mention what player you are using. Is it a drawer load, top load, or slot load.
If it is a drawer load you may want to remove the top and then use the canned air so that you can more directly aim at the lens. Same with a slot load. Hopefully it is something simple.
If it is a drawer load you may want to remove the top and then use the canned air so that you can more directly aim at the lens. Same with a slot load. Hopefully it is something simple.