ok so this is more common than you think its known as the open/close tray error,
Unfortunately there are several causes, it could be the lense needs cleaning, it may be the disk drive that needs re-alligning or just laser re-alligning.
It is a simple fix when you use a repair guide, i use XBOX 360 3 red lights fix, not only for the Red ring of death but for more common error's like yours,
Have a look at the guide and read everything it has to offer
Just go to http://www.dr-xbox.tk/ click on reviews and choose chris jones's read the full review before downloading the guide.
You can have an error free xbox guaranteed or you money back and for just $23.99 its well worth it