Diablo 3 kick me out to the windows randomly

It started to happen yesterday and a hour ago. I wonder what’s exactly caused it? Specifically, it doesn’t close when it kick me out. the game is still on the taskbar and I clicked it to go back in and continue playing in middle of the game. I’m little scared that may happen again because I play HC. it didn’t give me code and anything.

UPDATE:
It must be foreground and background FPS that caused my game went minimizing. Since I defaulted it, it doesn’t go minimised so far. Hope it’ll stay this way. sorry for waste your time. happy gaming

Long shot…
Windows Key + M is the keyboard shortcut to minimise the foreground application to the Taskbar. Is it possible that your Windows Key is stuck down and occasionally you press M to view the Map?

Another potential cause would be playing in Fullscreen mode, then clicking on another screen, causing the game to become minimised. Normally the game would confine your mouse to the game window, so you can’t move it to another screen, but some overlays or recording software can mess with that confinement.

how do you reply so quick here but i have made a forum post days ago and still not been helped? im literally stuck in this game

I simply hold on right click mouse to move around and next thing I know I am at the desktop out of the blue. I didn’t press anything tbh. My theory that hardcore mode may be the cause since I started it. I will give it a try again on softcore tomorrow