Sony Vaio Z21WN tuning off problem
I have a patient like this: a Sony Vaio Z series from 2008. It's a very nice, lightweight, small premium laptop from back then, but ever since I got it, it's been giving me a hard time. It was sluggish at first, so of course I gave it a 64GB SSD I found at home, unfortunately. And ever since I got it, it's been shutting down at random times. For example, sometimes it runs for hours without stopping. Sometimes I pick it up and it shuts down. Sometimes it shuts down while using it. Sometimes it shuts down when I move the display cover, and it's completely silent. It's generally loud, so I think the thermal paste needs replacing, but from what I've seen, it's relatively clean and well-cared for. When it sometimes turns off, it doesn't respond to the power button. A while ago, it turned off when I touched the USB port with a cable from a laptop cooler fan. So, what could be wrong with it? Seriously, it's a bit of a mystery to me. I'm afraid to open it up because it's a rare and expensive piece of equipment.
What do you think is causing this?