How did you try cleaning it?
Use a basically worthless Cleaning cd?
Or a cotton swab slightly wet with plastic eyeglass cleaner and the top
cover open?

Other people will say to use alcohol to clean the lens. I do not
because some manufactures claim it can damage the coating on the
plastic lens. Since I am generally lazy when it comes to looking up
which ones can use it and which ones say not to use it when all the
unit needs is an obvious cleaning, I use the generally accepted and
always safe plastic eyeglass lens cleaning solution.

Beyond that, the laser could be simply getting weak or the spindle
motor could be having problems.

Read the FAQ on cd players: www.repairfaq.org.