Computer CD-ROM drives are fairly robust and need little if any attention. They can function even with a fair amount of dust on the lens, but on rare occasions, may get dirty enough to require cleaning. Symptoms of a dirty lens include long read times, problems recognizing that there is a disc in the drive, and skipping or repeating on audio CDs. These symptoms are often intermittent and a CD drive may function perfectly most of the time and have only occasional problems.
These should never be cleaned routinely. Clean them only if you suspect a problem. The cleaning process itself carries a small chance of damaging the lens or other equipment. If only one disc is behaving badly, it's likely to be just that disc that is the problem. Even if several discs have problems, your first step should be cleaning and inspecting the discs rather than the drive. Here's how to clean a CD. Dampen a soft cloth or paper towel. Don't use a dry cloth as that may scratch the disc.
Wipe the disc gently from center to edge, not in a circular motion. Try just using water at first, but if that doesn't fix the problem, you can try a mild detergent. Never use abrasives or solvents. Dry with a lint-free cloth.