Hi Jcal,
Welcome to TSF
so currently you are still running and no shutoff yet after several hours. what you noticed all seem to point to an overheating problem.
do you use a cooling pad? by any chance you are running it on something that might cover the vents (like using it on a carpeted floor, or on a comforter, etc.)?
try to observe it first and post back if it will shutoff again.