Black screen, rapidly blinking cursor, no ctrl-alt-del

I am having a problem that- after the huge problem I had some weeks ago- have made me worried.

My pc is a panasonic notebook running windows 10. It is connected to a power plug that is somehow special- I don't know if that is the problem or not. (the plug disconnects itself after no use of some time)

Anyway, sometimes when I leave the pc idle for some time Without any warning, without any screen saver (by the way, does windows 10 still have screensavers, I couldnt find them) the screen goes black. any intent to do something makes the cursor appears as a arrow, blinking furiously. Nothing else can be done. No ctrl-alt-del or esc works.
The only solution is to turn it off and on manually. then everything goes ok until it happens again

sometimes if I leave it idle for a long time, I can recover it, but if I try to go again immediately after it went black, then it is all over.

How can I solve this?

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My traumatic experience I mentioned was that my brand new windows 10 machine went awful for a n entire week last time. I re-installed windows 10 like 5 times, and nothing worked. The machine was impossible to work . It took me 1hour and a half to launch one program. office was unworkable.

Turns out the problem was windows defender. It should have disabled itself automatically when another antivirus was installed but it didn't. I did it manually and now the machine works fast and ok (except for the thing I post above)

Open administrative command prompt and type or copy and paste these commands:

1) winver (in the pop up about windows view the windows version and build and post into the thread)

2) sfc /scannow

3) dism /online /cleanup-image /restorehealth

4) net user test /add

5) chkdsk /scan

6) When these have completed > right click on the top bar or title bar of the administrative command prompt box > left click on edit then select all > right click on the top bar again > left click on edit then copy > paste into the thread

7) shutdown /r

8) when the computer reboots sign on the new user named test

Check your computer for performance using the new user and report results into the thread.
If this does not work there are more steps.
Please make sure you provide details about the problems.

Also include any new hardware or software changes.
When problems started.
What you can do to alter the problems or make them go away.
The troubleshooting steps that you have already performed.