Dell XPS 15 - waking up re-positions all windows on external monitors

I do not have a dock, it is connected via HDMI port. Monitor is Samsung 27". And when I immediately log in back I do not have this issue. It is only after screen turns off (which is in few minutes).

That shouldn't be happening.  You didn't mention exactly how your external display(s) is/are connected to your system, though.  If you're using some sort of dock or other adapter, what specific dock/adapter is it?  And does this occur even if you lock your Windows session and immediately log back in, or does it only happen if you wait long enough for the system to turn off the displays, or do you have to wait long enough for it to go completely to sleep?

@Matt525252  ok, good data point.  In that case it might be something about the system firmware.  I suspected the display first because for example I've seen some displays where turning them off causes them to drop off the system, whereas other displays still remain present unless you physically disconnect their data or power cable -- although ironically in that scenario, the former behavior is actually preferable, otherwise Windows can keep applications on a display that's powered off.

Anyhow, if you haven't already, I'd suggest making sure you're running the latest BIOS and the latest drivers for both your Intel and NVIDIA GPUs.  If that doesn't resolve it, I'm not aware of anything you can configure in Windows that would affect how display sleep works (other than disabling display sleep, of course), in which case this might be an issue that would have to be resolved as part of a future firmware/driver update.

@Matt525252  ok, I suspect this will be the result of how the display firmware works. On some displays, when the attached system sends a signal to put the external display to sleep, the display will turn off its actual panel but keep its input interface active to remain "present" to the system.  But I suspect what's happening here is that your particular display is turning off its interface somehow, which is making it appear to the system that the display has actually been disconnected.  When that happens, Windows automatically brings any application windows that were on that display over to connected displays so that those windows aren't lost -- but it doesn't automatically put windows back ONTO that display even if you reattach it.  I admit it's strange to me that the display could sleep in a way that turns off its HDMI interface but can nonetheless wake back up automatically when you come back to your system (I assume that's the case?), but that would seem to account for the behavior.  If you wanted to test this, try connecting your system to some other HDMI display or TV and see what happens.  I suspect that with at least most other displays/TVs you test, you will NOT see this behavior because they'll keep their interface active specifically to avoid this type of issue.

But it is strange as I also use this monitor with HP laptop and Mac Pro and do not have this problem with them.

I don't think that will solve anything, but the way to uninstall those drivers is inside Programs and Features, not Device Manager.  The Intel and NVIDIA driver packages will both have entries there.  And yes your system will still be usable after you uninstall those drivers.  External displays may not work until you reinstall them, but you'll definitely still be able to use your system because Windows loads a default generic graphics driver when it doesn't have a driver specific for your GPU(s).

I tried that and it did not help at all. I think the problem has two parts:

1.) I have set sleep when plugged in to "never" but when logged out this will happen anyway in 2 minutes even when plugged in.

2.) After going to sleep, the monitor is disconnected and windows positions are lost. I do not know if this is a bug or feature... But anyhow it does not seam right.

So I was actually even able to set system unattended timeout (using this solution: https://superuser.com/a/1186786) when plugged in from 2 minutes to 180 minutes (then restarted of course) but it still goes to sleep in few minutes and losing all windows positions. I will try to solve it with customer support and if I fail to fix it I will be probably forced to return this device and get something more reliable. Their last message was that it could be due to magnetic interference, which I do not think is possible with my setup.