"Fishing in the dark" a bit, but I'd wonder if the HDD is a bit slow in spooling up - doesn't "get there" when the system is first switched on, but is up to speed by the time the reset button is pressed - any takers?
Another thing which I have found to cause "strange startup" is a system plugged into a 100volt supply but the switch on the power supply at the back of the system box selected to 220volt. Not sure where you live, Oleo, but if outside Europe this might be the problem.