I just recently tried to open the box and use a home fan on it and I can run games now. It must be a GPU overheating. Compressed air to clean the dust will do the trick right?
now you find out,, cleaning might help but also check other system neccesity, your cooling system might not be enough
for your gaming requirement,, enhance or upgrade your cooling system... you said your gpu run about 75 for me that is high..