This *could* be your Hard Drive. I know when my iBook G3 (Dual USB) started having problems, it took it forever to boot up and I had the exact same problems. My hard drive didn't die for a few months after that, but it was a sign. Run the Mac hardware check, then backup everything so in case your HD does fail then you are fine. I can't give any recommendation other than reinstalling OSX to see if that will fix the problem.