Hi Elly,
First things first. Remove the top cover and check if the laser is seated properly.
If yes, place the top cover back, but make sure it seats good!! It should fit in flawless. And make sure that the laser is not blocking the case from seating (as this happens sometimes).
If this is all good, place the screws back and try it. Also, check if the disc can spin freely and is not spinning against the cover.. This would make scratches and it will stop spinning after 10 seconds.
How is the condition of the drive motor/disk holder?