Yep, already advised that!
You can speculate and theorise till the cows come home, at the end of the day you have to start proving or disproving some of these theories and you can't do that if you have 'unknowns' in the mix.
It may well be a faulty PSU, but variable and inconsistent startups are often due to the board capacitors not holding any or little charge and that sucks power out of the board causing inconsistency. You won't know that of course until....you replace the PRAM battery!
Full circle!