While working the system is overheating and turning off

Lets see if we can better identify the problem

Restart your system and press the D key to enter into the onboard diagnostics. Did you get any errors?

Reference: Mac startup key combinations

I would also install a good thermal monitoring app like TG Pro as it will allow you (and us) to see more clearly what is overheating.

Given the systems age you also likely need a new battery. When a battery gets old it often needs more charging which in turn causes the power logic within the logic board to heat up. To get a better view of what's happening within the battery install this app CoconutBattery.

Take a snapshot of the apps main window for both and post it here for us to see Voeg afbeeldingen toe aan een bestaande vraag

Also what are you doing on your system - Workflow ??