cd player not reading a disc? Laser dirty?

Will it play other disks or just not the one that was already in the transport? Also, do you leave your CD player powered up all the time or turn it on for each use?

It is erratic. Sometimes not the one in the disc; then may not play another I have played recently. I may move the disc in the tray and it may play after 1 or 2 attempts; or I may put in another disc and it plays. Only happens with CD's not DVD's.
DVD's always play...?? It is frustrating.

I think its all going to depend on what kind of transport the unit has. I can't see the problem being anything else. It sounds like the laser may be dirty, as you suspect, or possibly something to do with the tray itself. Given the fact that you sometimes get the disc to play after you move it in the tray. I don't know what player you have, but I think it would be a pretty safe bet to try and locate a new transport. If you are not afraid to open the unit up, its probably a part that you can easily replace yourself.