It could well be a motherboard hardware issue. Possibly with the temperature sensors.
Just remove the battery and the power brick, press and hold the power button for 20 secs or more. Then see whether it clears.
Also check whether your fan is not clogged with dust and quite free. If you do have a multimeter check whether the power brick delivers the correct voltage.
One more thing you can try is to remove the battery, power it only from the brick and test.
You can update the BIOS if the notebook works that long to finish the update.
