From the sounds of it your system is over heating! But given its age your battery maybe the issue as well.
Let’s first remove the battery question. Install this gem of an App it will allow you to see the battery’s state [https://www.coconut-flavour.com/coconutbattery/|CoconutBattery] take a screen snapshot of the Apps main window pasting it here for us to see.
The next action is to install this great app so you can monitor your systems thermals and fan [https://www.tunabellysoftware.com/tgpro/|TG-Pro] let’s see what it tells us, again post a snapshot when things are just about to fail.