My Mac Pro starts up when I turn on the power, BEFORE I switch it on with the button, why? Plus, my computer keeps freezing and blacking out.

Question

My Mac Pro starts up when I turn on the power supply (when I plug it to the outlet), BEFORE I switch on the button on the computer, why is this happening? Plus, my computer keeps freezing and blacking out and I'm forced to restart it, that's when the compter starts on its own when I turn on the power.

Answer 1

Hello Engender,
I should have followed up with a progress report because I eventually eliminated all the problems I was having with my Mac Pro, now it's behaving like a new computer… beautifully.   I did originally take Grant's advice above, changing the setting that I had in the System Preferences > Energy Saver but that only stopped from rebooting on its own when I shut down my Mac properly.  Otherwise it continued to restart on its own after freezing or crushing when I switched on the power.  I took my machine to the Apple Store and after many tests they couldn't find anything wrong with it.  I was very depressed about the whole business.
It was after going onto many of the other Apple related websites that I discovered that it wasn't a faulty power switch or fan, as as I originally thought, but found out that my problem was related to the Graphic Card and possibly I did not have enough ram (I had the original amount of 2 GB).  The original card that came with the computer: 512 MB ATI Radeon X1900 XT was over heating and forcing my machine to shut down, I think it was because I had upgraded to OSX Lion which on its own requires at least 2 GB of ram to operate well.  I added 4 GB of Ram to the 2GB I had (4GB kit (2GBx2), Apple 240-pin FBDIMM, DDR2 PC2-5300 upgrades for Apple Mac Pro (4-core) 1st Gen. - 2006-2007 Desktop/PC, CT579443 from Crucial.com about $160 for the set) and replaced the Graphic Card with ATI Radeon HD 5770 1024 MB from Apple (around $260), (ATI Radeon HD 5770 Graphics Upgrade Kit for Mac Pro (Mid 2010) - Apple Store (U.S.))  This card works very well with my original Mac Pro 2008.  I installed it about two weeks ago and no problem with it starting on its own, over heating or freezing.  OSX Lion works well and I'm thinking of upgrading to Mountain Lion once I learn that my Mac Pro 1.1  will work with the new hardware I installed.
Your problem could just be the power cord but I agree with you that doesn't sound right, when I mentioned faulty switch I meant the part where the power cord meets the power button, the unit which houses the power distribution, I thought at first that it could be faulty but changed my mind because of the computer overheating. 
I don't know if this is of any help to you but I hope your trouble will be solved with the new cord.