The laptop sometimes turns on, and hangs for 0-3 minutes. What could be?

Question

Iron

Everything worked yesterday. Approximately 1 time out of 10, the laptop starts, checks the memory, everything is fine, it hangs for 0-3 minutes.
I suspect the video card, it often heated up with a load of over 100 when I forgot to turn the cooler out of quiet mode. Yesterday, too, she was very hot, probably about 100.
DVD, HDD removed. Memory poked. The result is the same. In other cases, a black screen.
The cooler is working, but it does not start, it is strange that on yellow + black 3.25 volts, on red + black 0.25 Is that how it should be?
If this is a video card, then why does the laptop sometimes start up?
Still, it looks like memory problems, although I have already changed 3 bars, or video card memory.
Hangs not because of overheating, at the moment of freezing the radiator is not hot .
Please help. The laptop is old, but very comfortable like old Thinkpads, I don't want to throw it away and buy a new buzzing plastic shit.

Answer 1

Have you been cleaning for a long time?
Does it work without a cooler?) How is it?