Has any one seen this before with an apple pc. I don't know what it is other than a new pc. A customer of mine is complaining of power problems because her apple keeps rebooting on it's own. I have checked the voltage/frequency & see no apparent problems. Being a windows man myself I do know that apple can have their quirks also. It does not do it all the time, maybe once a week. The pc has been back to apple & they say it's ok. I suggested they put a windows machine in this out let & see if it does the same. They refuse. They bought a power bar with filtering on it & it still did this. I was going to put a trace on the power for a week & see what it does or doesn't show. Do apples have a bios? Could some setting be causing this? I'm at a loss.

No, not in the traditional sense you're thinking of anyways. Someday PC's won't have one either. A bios is considered a clunky way of handling hardware functions and the computer industry wants it gone eventually.
You can access certain hardware functions though. See: Open Firmware
I use to work for an authorized Apple repair shop but that was back in 1992. I wouldn't attempt messing with system settings now until I was absolutely sure of what I was doing. Probably childs play for a mac enthusiast though.
The symptoms do sound hardware related. I'd be looking for a pattern here. Does it always reboot using a specific program, does it do it only after it's been on for a certain amount of time, etc.
One things for sure, if it was mine and a new system, Apple would either be replacing it, fixing it or wearing it.