MacPro shuts down by itself after start up

[oreocracker]

This only happens when I first boot up. After about 10 mins, the computer shuts down and reboots itself. Sometimes it sounds like a car engine trying to rev up. (It's not loud, just has that sound) Sometimes it does it 3 x's in a row. Once it stays on, it stays on all day. It only does this when I first boot up in the morning. I can shut it down during the day, walk away, restart and it's fine, but it sometimes repeatedly shuts down first thing in the morning. Does anyone have a clue?
MacPro
2 x 3.2 GHz Quad-Core Intel Xeon
10.6.4

 

[CaptainChunk]

This only happens when I first boot up. After about 10 mins, the computer shuts down and reboots itself. Sometimes it sounds like a car engine trying to rev up. (It's not loud, just has that sound) Sometimes it does it 3 x's in a row. Once it stays on, it stays on all day. It only does this when I first boot up in the morning. I can shut it down during the day, walk away, restart and it's fine, but it sometimes repeatedly shuts down first thing in the morning. Does anyone have a clue?
MacPro
2 x 3.2 GHz Quad-Core Intel Xeon
10.6.4

Have you tried resetting the SMC (system management controller)? Sometimes, that will cause issues like you're describing.

You can also try resetting the PRAM, too.

If none of that works, you might want to call AppleCare if you're still under warranty.

 

[Maury]

This only happens when I first boot up. After about 10 mins, the computer shuts down and reboots itself. Sometimes it sounds like a car engine trying to rev up. (It's not loud, just has that sound) Sometimes it does it 3 x's in a row. Once it stays on, it stays on all day. It only does this when I first boot up in the morning. I can shut it down during the day, walk away, restart and it's fine, but it sometimes repeatedly shuts down first thing in the morning. Does anyone have a clue?
MacPro
2 x 3.2 GHz Quad-Core Intel Xeon
10.6.4

Your graphics card may be overheating. What type is it?

If it's anything with oomph, get SMC Controller and bump up the speed of the fan in the card bay a little.

Maury

 

[oreocracker]

computer rebooting spontaneously

I finally sent it to the Apple Tech shop near me. They couldn't find any firmware issues, so they ran diskwarrior. DW stalled out, so they thought. The next day they ran it again and let it stay in what they thought was the 'stuck position'. Evidently, it was working on something in the background. Hasn't spontaneously rebooted since. Keep your fingers crossed for me.

 

[CaptainChunk]

Also, have you tried running the Apple Hardware Test? It should be on the Applications disc that shipped with your Mac Pro. You would hold down "D" on the keyboard while booting with the disc in the drive. I'd be curious to know if any SMC errors are showing up.