Mac Pro (Early 2008 Model) boots itself up...please help!

This happens whenever I switch on my wall socket. It automatically turns itself on without me pressing anything...is anyone able to explain this and give me a solution?

I have run the PRAM and NVRAM Reset test but this did not solve the problem. I attempted to run the SMC Reset test but am unable to wait 5 seconds as per step 5 (see 'Resetting the SMC for Mac Pro' section at Intel-based Macs: Resetting the System Management Controller (SMC) ) - when I re-attach the power cord back into the machine, it boots itself up immediately.

Thanks in advance!

I refurbish said to be dead Mac pro's and 2 instances I have noted with auto powerups upon plug in is either is a bad CMOS back up battery, bad memory card or bad memory riser. First replace the neglected back up battery flat lithium CR2032 then test. No success? Remove both memory risers and only place the memory cards that originally shipped in one riser. Install just the one riser in top bay and restart. No success? Try the second memory riser in the same fashion explained above. No success, you will need to verify memory cards are good. You will most likely reach success with replacement of the back up battery.
Post your results. Thanks

@OP I notice that you mentioned switching on the power outlet. Check your Energy Saver preference pane. At the bottom of the list of settings is an option to have the machine "Start up automatically after a power failure". If that setting is turned on every time the outlet is switched off the software thinks there has been a power failure and will restart the machine as soon as power is available again.

Well, believe it or not, I plugged the power cord from the Mac Pro directly into the wall and it behaved normally!

Must have been a dodgy surge protector...I will keep the machine connected directly to the wall socket from now on..

Thanks for all your input

The Mac Pro should be fine attached to a surge protector as long as the surge is good. I have my '07 model on one all the time. You can even turn the outlet off as long as that setting Isn't checked.

If I owned an expensive Mac Pro, I would have it hooked to an UPS. ;D

Well..after being overly emphatic I can now tell you that I spoke too soon!

Looks like plugging the power cord directly into the wall has not made a difference...turned it on at the wall today and the Mac Pro booted itself up again!

I am going to buy a new lithium battery and replace the old one. Will keep you all posted.

Thanks again!

EDIT: @Slydude - this option has always been unchecked...thanks for the suggestion though.