1. fan problem due to cpu overheat. the system protection activated!
2. transformer problem, is it too old? capacitor dried out
3. Ram problem but might be becos u can see the "window"
clean the dust on fan, making the cpu fan firm + colling agent
if cant solve, you have to follow my experience >>> buy the new transformer!
my previous case same as yours, finally, I buy the new transformer and problem solved!