[SIZE=2]Most likely the CD drive in the system is starting to go-mine did the same thing after 5 years of faithful service.
Your options are these:
1. Find a replacement laser unit and have it replaced.If you can't find one locally at a game store it is fairly easy to find online.
2. Buy a PSOne (considering the cost of the laser unit and the charges to have someone install it this may wind up being the cheaper option)
3. Upgrade to a PS2.Considering the lack of games coming for the ol' PSX you may want to consider making the jump-you wouldn't even have to get rid of your games as they will work in the PS2.[/SIZE]