iMac G3 randomly shuts down

[JCLrox]

I just purchased an indigo 400 MHz iMac g3, and noticed that after it's been sleeping for about an hour, it randomly shuts down. The first time I noticed I was out all day, so I couldn't see how long it took for this to happen, but now I think it took about an hour. Does anyone know what could cause this? Could I fix it? I know it's an old machine and it's bound to malfunction, but I had some plans for this thing. Thanks for any help you can provide.

 

[Intell]

It turns off as it's sleeping? Or does it turn off after you awaken it and use it for a while?

 

[JCLrox]

It shuts down as it's sleeping. I might use it for say, 20 minutes, put it to sleep, then it will shut down. I know it was sleeping for a good bit of time because I saw the power button glowing. I have to go to sleep, I will reply in the morning.