get some rubbing alcohol and clean the laser lens with q-tips. make sure that you don't scratch the lens or leave fingerprints on it.
make sure that the parallel roll bars where the laser sits to move and up & down has enough grease (white lithium grease i think).
you could also try to adjust the laser if needed. check out this link for instructions. http://www.ps2parts.com/laser_adjustment.html
if all fails, then conclude that your laser is about to give up and you'll prob need a new replacement. check out ebay or www.ps2parts.com for parts.
i'd highly recommend googleling "the romeo mod" to apply as you fix the laser because this mod prevents any damage done by the design flaw in console versions 9-10 (which frys the laser & LA-6508 chip). my v.9 console already met this fate and i have to fix it.
PS1/SCPH-7501 | MM3 modchip
PS2 v9 | 250GB hdd | PS3 component cable | katana 32mb mc
PS3/CECH-2001B | 250GB hdd | 3.65 ofw