Question Laptop randomly turns off and on

Jun 30, 2019
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Hi everyone.
I know there are many threads regarding my issue, but there are several issues that I can't really put together. So.

Laptop was working fine, regularly cleaned, never overheating. Few days ago I did Win 7 update, it was succesful, it shut down normaly. Few days after I turned it on, few seconds and it shut down. I tried again, same thing happened.
Then I went to BIOS, did absolutely nothing to settings, and Windows started normaly. Laptop was fine that day.
The next day, same thing, but I couldn't start it like I did day before. Then it shut down. After few minutes it turns on by itself, instantly, shuts off, then repeat.

I opened it, checked everything inside, I even replaced the paste on CPU and GPU, and put everything back. Ten I tried again. It shut down. I tried again, it booted to Windows. Ok. It was on for about 15 minutes. The display goes dim and shuts down. I tried again. It booted fine. Then I decided to check for errors. None were found. Then I reinstalled the Windows. (I was always interrupted by random shutting, except when reinstalling, that went just fine). And now I'm back to beggining - can't boot to Windows anymore, most of the times doesn't even reach the BIOS point.

So, everything is clear, no overheating, it is charging normaly because the MOBO light says so, I removed RAM stick by stick (2x), nothing, I removed HDD, nothing, chkdsk gave nothing.
Sometimes it turns on, shuts immediatly, sometimes shuts after BIOS, sometimes boots up, then randomly shuts inside Windows, and sometimes is just fine.

Any ideas, what to do with it anymore? Because I really don't know what happened to it. Don't know is CPU is thinking about dying or not -.-

Thanks in advance!
 
Jun 30, 2019
3
0
10
Make and model laptop? Age, condition?

Laptop hardware specs - especially PSU?

Toshiba P750-10N, bought 2013 (I have Toshiba P770 laptop, bought 2011, works just fine). As I said, regularly cleaned, changed thermo paste, never reached overheating point and is not overheating now when I enter it.

Specs:
Windows 7 Home, 64-bit
Intel i5-2410M, 2.30-2.90 GHz
Originally 4 GB RAM, expanded it to max 8GB (tried removing added stick of RAM, nothing)
HDD 500GB (SSH + NAND flash) 7200rpm
NVIDIA GeForce GT 540M + CUDA, 2GB VRAM
TOSHIBA PSU PA-1900-35: input 100-240V, output 19V=3.95A
 
Jun 30, 2019
3
0
10
Toshiba P750-10N, bought 2013 (I have Toshiba P770 laptop, bought 2011, works just fine). As I said, regularly cleaned, changed thermo paste, never reached overheating point and is not overheating now when I enter it.

Specs:
Windows 7 Home, 64-bit
Intel i5-2410M, 2.30-2.90 GHz
Originally 4 GB RAM, expanded it to max 8GB (tried removing added stick of RAM, nothing)
HDD 500GB (SSH + NAND flash) 7200rpm
NVIDIA GeForce GT 540M + CUDA, 2GB VRAM
TOSHIBA PSU PA-1900-35: input 100-240V, output 19V=3.95A
Additionally this morning, I tried turning it on, and now it shows TOSHIBA logo for reaching to BIOS and afterwards shows black screen with blinking cursors, and then shuts after few seconds.
Next time it turned on by itself in few seconds and shut down before reaching windows.
I tried with battery only, without battery only charging, together, it is all the same.