Hi!
My E350M1 start automatically after a electric cut. I tested this in the hope but I get the same result: http://review.coreboot.org/#/c/5397/
That (hopefully) fixes a completely different problem.
Does watchdog is used by default?
That doesn't sound like the watchdog.
Do you have an idea or solution?
Have a look at the power loss control bits inside the superio chip. They specify what to do when the mainboard gets its standby power.
Regards, Felix