Start menu lag caused by switching the GPU

Hello
I installed a fresh copy of Windows 10 v1903 on my ASUS N53SV laptop. I updated drivers using windows update.
I noticed that every time I try to open the start menu, It shows after a small (say half a second) lag. If I keep pressing start key, the subsequent openings are lag free. But if I wait for a few seconds and try to open start menu, the lag happens again.
I also noticed the lag is concurrent with color change of GPU indicator light. Every time the lag occurs, current GPU changes from Intel HD to dedicated Nvidia GeForce for a brief time.
I tried to track GPU switching using Nvidia GPU Activity app, but it doesn't show any app using dedicated GPU (maybe because it switches back to Integrated GPU shortly)

I tried the following too:
- in nvidia control panel, changed the default graphics processor to Integrated.
- added explicit rules to use integrated graphics for searchui.exe, dwm.exe and startmenuexperiencehost.exe

The only solution which is not optimal is to make nvidia the default GPU.

Can you help me track the culprit?

What you are seeing is normal operation, the GPU which may/may not be the one used at the time is irrelevant.

The minor lag could be due to Caching, Pre-fetch, Super Prefetch, Priorities etc.

I set my Global Settings to Auto-select graphics processor.
The Program Settings list is added to when I think it is necessary and make Nvidia the preferred GPU.

The Nvidia task bar icons are switched off, prefer to use the Task Manager as the indicator. Though you apparently need WDDM 2.0+ for that.
The Nvidia GPU activity App, or Geforce Experience are bloatware.

The things you mention I would not bother with configuring, far too insignificant.

To prove my point, I completely disabled Nvidia GPU from Device Manager. Now there is no lag.
I think that I'll keep it disabled, as I really don't need GFX power. I use start menu indexed search too often and prefer not to have lag .

I uninstalled the Nvidia driver provided by Windows update and installed the latest from Nvidia website (unchecked geforce experience and physx); now everything looks smooth: no GPU switching and no Start menu lag!
The problem seems to be fixed for now.