Your PS3 may'be close to having the YLOD. Your problem is probably your motherboards thermal paste try adding some to it or it might be the whole motherboard thats close to messing up.
Microchips don't actually lag. They all run at a very precise speed, or not at all, generally. The most likely cause is that you hard disk is failing. You can replace the hard disk yourself, and it doesn't even void the warranty.