This system had issues with bad capacitors [https://en.wikipedia.org/wiki/Capacitor_plague|Capacitor plague]. It likely needs a new power supply as well as PRAM battery.
Now the real question is if its worth fixing? This system can’t run anything newer as it was based on the RISC chip architecture of the IBM PowerPC chip. Todays systems use the CISC based Intel processors. As its so old it won’t work with your iPhone or iPad with the latest firmware on them.
It you need a new system I would look at a used 2011 or newer iMac or 2012 or newer MacBook Pro.