Reinstall os and all games. A full reinstall of the os is the only way to fix this.

Do you have multiple displays? If you have multiple displays and depending on how you have the game configured you may push the cursor beyond the bounding box and click on the other display which will change focus to that display and seem like an alt+tab.

Try changing the window mode Full screen exclusive if you are running it in borderless window mode; or vis-a-verse and see if it is still happening. If it's only happening in newer games if they are all running dx12 that doesn't use full screen exclusive mode and will automatically be running in borderless mode. You could try switching to Vulkan if the game supports it to see if the window binding for the cursor works better for those games using that render.

Something in the background is taking focus
Easiest way to figure out what is 1: Close any unneeded programs/processes before gaming, or use the task manager to see what else besides the game and system processes are being utilized.

A Full reinstall is Not Necessary, you just have to figure out what is taking focus from the game.

disable everything in windows startup dn reboot
then try again

maybe the keyboard. just saying. can you swap keyboards with another to check

I had a Razer mouse that got a firmware virus. no joke.

Have you checked windows shortcuts/hotkeys? maybe one is conflicting with game cmd's.

RUN SFC

引用自 PopinFRESH：

Do you have multiple displays?

I don't, I only have one display

引用自 ☥ - CJ -：

: Close any unneeded programs/processes before gaming, or use the task manager to see what else besides the game and system processes are being utilized.

I will try this out and see

new mouse ? if you have side thumb buttons the rear one is normally by default
set to ALT TAB..

Im sorry for necroing, but in my case it was Wallpaper engine. Occured to me while reading this thread concidering i had the same problem. Every 2 hours, also the same time my walpaper changes