[Techtalk] computer starts wrongly

[Alvin Goats]

I had some similar problems, then the real time clock started to act 
up... try replacing your MB's battery. It does some micropower status 
that is used by the power supply system to help indicate the front panel 
switch condition (was it on or off) and other things including the real 
time clock. With insufficient power, it can get confused about what the 
state was and do things like you describe.

The batteries are only rated to last about 3 to 4 years, so it should be 
time to replace yours.

The battery is the cheapest thing to check out, so I'd do it first 
before going to far.

Hope this helps!

Alvin