Had two 2007 MacBook Pro's break down that way. Local Apple Care Service providers didn't want to apply Apple-mandated extended warranty. I was pretty disappointed to find out that later models exhibited similar flaws, because the soldering issue of 2007 models was blamed on nVidia.
When a friend was buying her mother a christmas present iPad, I went with her to examine which models handle the tablet workload better. We ended up picking an older generation, non-retina model. A few previous generation retina models, presumably running latest iOS updates, had ridiculously high temperatures just idling on the shelf.
Nvidia made a run of defective GPUs somewhere around 2007-2008. Tom's Hardware claims[0] that all G84 and G86 GPUs other than warranty replacements produced in late 20008 are defective.
It's not a BGA solder issue like we've seen on numerous laptop GPUs over the years, but a problem with the internal interconnects. Heating it, as if to reflow a BGA does temporarily solve the problem, but in my experience, the period of time it keeps working after heating gets shorter each time.
https://www.change.org/p/timothy-d-cook-replace-or-fix-all-2...
It's ludicrous that to attempt to fix this problem, you would have to go so far as to bake your laptop.
It cost me over $US 500 to get this fixed at an Apple Store.