I7-950 Computer Frequent Shutdown Problem

Frequent shutdowns, I7-950, where to start?
I have an Apple DX58S0 and i7-950, NOT overclocked, created about 18 several weeks ago and has been firm.
The last two shoes after it was off and freezing it has totally reset itself every few moments. It operates for a while (increasingly extended each time), then reboots.
There are no components issues in the bios, there are no function log items of desire (other than the "was unexpected"), there are no obvious symptoms and symptoms on the display, and no beeps or uncommon tones. I ran the CPUID Hardware check once and as it totally reset conditions were great and standard (mid Fifties c). It is basically as though the totally reset switch was hit.
I have started out it up and while going shaken and ripped every connection and greeting card without result. I have booted house windows (7 x 64) into secure method and it still neglects (plus there are no symptoms of a glowing blue display or different logged). Before, once it was up and seemed secure, I ran about 12 time of storage testing without problem (not that I especially thought storage but thought that was a great mid-level load).
Last time after lastly being up, it kept up for about two several weeks without issues (I usually depart it up except when travelling). Now am on about the 8th footwear, not sure if it will keep up.
I've seen the situation when it reboots (a bit difficult to get in the act as there is no warning), and I did not observe any flicker in the signals on the followers, just the fan speeding up as it does when it first shoes. I cannot claim I would have seen a brief flicker as you have to look anywhere up to about an time and I don't quite have that desire period.
With no symptoms and symptoms other than a system — not sure where to begin. Any recommendations? I'm considering energy, but I do not have a great additional (I have one, but it is an old 400W and not sure that is ample but may try it anyway, it is close). Currently trying it off the UPS, but not encouraged there, no explanation to think it.