Question Powershell window popping up everytime, one hour or so after a startup.

I didn't see any script running in the Shell, so your PC is presumably safe. Still, see if disabling PowerShell can present you with an error to point you in the right direction: (I plagiarized the info below from https://www.makeuseof.com/windows-disable-command-prompt-powershell/ so I wouldn't have to type out the steps)

  1. Press Win + R to open the Run command dialog box.
  2. Type gpedit.msc and press Enter to open the LGPE.
  3. Navigate to User Configuration > Administrative Templates > System.
  4. Double-click on the Don't run specified Windows applications option on the right-hand side pane.
Next, select Enabled in the top-left corner. From there, navigate to the Options section in the bottom-left and click the Show button. This should pop up the Show Contents screen.

Type powershell.exe below the Value box and then press OK. Next, press Apply and then press OK in the LGPE window. This should disable the PowerShell tool.

Note: There are more services/applications that have dependency on the above-mentioned configuration, so leave the LGPE open after applying the steps so you can easily reverse the steps.