Hi Andras,
I believe that the problem is associated with the Jupyter Notebook extension/module which I added to Slicer. Let me describe the auto start problem in some detail.
The automatic restart of Slicer does not happen when I start my PC. Nor does it happen when I start Slicer from Windows start menu and close it again.
When I use Slicer from a Jupyter Notebook in Anaconda (attached), the Slicer function in the Noteboo works perfectly, and at the same time the Slicer app starts with the Welcome screen as module. After closing this Slicer instance (subsequent to closing the Jupyter Notebook and Anaconda), Slicer restarts automatically some 10-15 seconds later. This pattern repeats until the PC is restarted.
I noticed that the Slicer icon in the Windows Task bar shows the following contextual menu:

When I tried to activate “SlicerApp-real”, I received the missing files error messages previously sent.
To your questions:
Latest Slicer download from your home page 4.11.20****
Slicer start: see description above
Windows 10 Pro 10.0.19041
Only new extension added to any program since start of the problem: SlicerJupyter module.
No new paths added to any program since start of the problem
Best regards,
Poul
(Attachment Poul_3DSlicer1.ipynb is missing)