Imac won't go beyond grey apple screen

Hi everyone:
I'm new to this board. Looks prettty cool!
I have a imac problem that I'm hoping one of you can help me with. Just recently, when I have my Imac G3 off for a couple of days, it will not go beyond the gray apple screen with the propeller thing (it runs OS X 10.2.6) when I turn it back. The only way I can get it to launch into the OS is to turn off the power strip the mac is plugged into. It eventually will go into the operating system and runs fine. This problem only occurs when I leave it off for two days or so. I tried leaving it off overnight and trying it in the morning, but it started up right away.
Any ideas?
Thanks
Noel

try resetting the PRAM (parameter random access memory) by holding down command (apple key) + option + p + r on start up. continue to hold it down until you hear it chime twice, then let go and it will go onto to startup normally.

after that, maybe let it go a few days and see if the problem persists.