aside from the edo real problem
your pc should not struggle just downloading HD anything.
I dl all my tv shows, I average 500gb a month, my main router used to get very hot and shutdown or reboot often
I have 3 routers and 2 5 port switches on all the time..i have a lot of devices.
if the router is getting bad blocks and failures, the pc keeps requesting, at a certain point the pc starts to spend too much effort on getting the data. you can watch this in the log of the router.
there are very many net devices that crater the hotter they get and most do not have fans and they should.
there are net devices that crater due to bad firmware and require constant resets to function at 100%, my newest ZTE 279 smarthub does both
it is counter fail in the firmware, very many zte owners are reporting this issue. It gets so hot that the battery shuts down, then the whole device becomes a paperweight till you shut it off and cool it down . it shouldn't, but it requires the battery to function. even though it is plugged in and charged or charging. remove the battery and it will power on, then right off again.
Linksys released several devices 5 years ago that crater often exactly the same as this zte, at a certain point the counters hit max and do NOT wrap or reset and dl/ul ratio go to 0%. at this point just accessing the GUI takes extreme patience, but it is fastest to simply power off, wait and repower.
the Linksys issue was so bad, I bought 6 different ones and finally bought an ASUS router to get away from the problem. that year I spent over $5,000 on routers just to get ripped off on all but 2 devices
I also installed fans in all of them to avoid the death by heat and the longevity by slow death by heat that is inherent in all of todays routers that have no fans.
I would buy a new router that has temp sensor and fan, just like a pc, they are required. But router manufacturers would rather we just keep replacing them.
As long as it is only the temp that causes it to slow or shut down, you can fix it by adding fans. since I have been doing this, I no longer have any router issues.
I have dozens of dead routers, all of them died for the same reason.
I have 3 very good routers that I put fans in, now 5 years old and still at 100%, this is a first for me and I am very glad I discovered why they kept dying.
just a thought and worth monitoring to see if its part of the problem you are having.
P.S. I should add that if you are not using a router, you should, otherwise you are doing the damage to your NIC instead, even if you use a router it doesn't hurt to add a fan on a desktop to keep the NIC or nic's cool. my gigabyte MB's have this because I do not want them fried either.
for a laptop, you can get cooling boards to sit it on, or like me when I am at home my MSI has 1 pc fan on its table on each side and one at the back all sucking air out. they are super quiet and you can feel the heat they are removing. as all my devices, I expect they will live much longer than the average users devices.