First check if your fans are making any noise on high speed or if they are working properly and their bearings are not faulty, then turn the laptop off from the power keyboard key, disassemble the back of the laptop and take the main battery out, the bios battery out and shorten the +&- mobo pins of the bios battery, take the ram and SSD M.2 drive out, leave all components disconnected for at least 30min and when you reconnect everything, make sure that the ram modules are swapped from their slots e.g. put ram module from slot #1 into slot #2 and vice versa, as this will do a hard reset of your laptops Super IO chip, bios chip and will diagnose if your ram is faulty also,

make sure that before you do all the above, you have ordered and have new paste and thermal pads, and take the thermal module out and clean the thermal module and cpu/gpu of all the old paste and take the old pads out and replace the cou/gpu paste with a high grade paste and replace the pads with either the K5 liquid paste pads solution or a cpu/gpu pads from Thermal Grizzly as they make a great high quality thermal paste and pads product for high end PCs, don't use Liquid Metal cpu/gpu Solutions. Try all that and see if that will solve your temp problems

CPU/GPU don't take long to cool down and allow usage, especially since thermal shut down initiates when the threshold is reached and not further.

It sounds more like a battery issue than a typical thermal shut down.

Have you inspected the battery to see if it's swelling?

The blue heat exchangers around the fan compartments suggest that the thermal module tubes to the CPU/GPU heat sinks are filled with liquid coolant. Not air cooled. The CPU's tubes might have developed a coolant leak if re-pasting failed to bring the CPU temps down. Themal pads were not used according to specs, Google search the heatsink module part number 24.Q6WN1.001 if it needs to be replaced.