I don't know why you have an ignore on your thread title but I thought I'd respond to see if the thread has been resolved.
I've worked on the laptop since a friend owned it and had me fix it for him. By turning off, does the issue happen when you're powered off the power brick/from the wall or when you're on the battery? If the latter, then it's highly possible that a replacement battery is necessary. If the laptop turns off while powered by the adapter/from the wall and the battery is removed, then it's possible that the laptop might be having a thermal issue(overheating) or that the motherboard's power regulatory components are showing heir age and are failing when taxed with power input.
If it's thermal issues, you can try replacing the thermal paste, clean the exhaust vents and see if the cooling fan needs replacing.