Mac OS X 10.6.8 randomly restarting?

[x87]

I have a mac pro 1.1 updated to 2.1 firmware running snow leopard. Every now and then the computer just restarts itself randomly. It isn't a kernel panic, there are no signs of any slowing down or glitches before this happens, just all of a sudden, BOOM, it has restarted. What is this about?

 

[Fishrrman]

I'm thinking...
"hardware".

 

[Gregg2]

minor power surge?

 

[STS Australia]

Try resetting the SMC controller. It's a tiny button under one of the PCI slots, hold it down for 15 seconds. Battery probably needs replacing too. I've got a 1,1 as well, running El Cap, definitely holds it's own against modern Macs in many ways.