It would help to know what phone you have, from where, and what version of Android it's running.

 

stay away from certain apps. some apps if you are not careful will come with adware which can potentially install other apps and ads onto the phone. read what permissions that app will have before installing them.

this is the only way to prevent such a thing from happening.

you will have to uninstall any recent apps to find out which app it came from. start with the most recent and work your way backwards.

 

Is this perhaps related to something called "instant apps"? This is a feature Google added a year or two back, and which I'm hoping they'll lose interest in and discontinue same as they do most things (since I saw more risk, or at least potential for annoyance, than benefit in this). Try searching your Settings for any mention of the word "instant" and turn off anything related to that that you can find.

In my s21 there is a toggle "upgrade web links" which allows links to be opened as "instant apps" rather than in a browser. I made sure that was turned off the day I got the phone. It lurks in Settings > Google > Settings for Google apps, but the search function is a quicker way of finding it.

My list of installed apps included something called "instant app engine", a name that would imply that this was the thing that ran instant apps (though it seemed to be one itself, which was strange). I "cleared" (i.e. uninstalled) that when I found it.

 

Thanks for the information!

 

There's a setting in the playstore app "settings > general > google play instant". You can disable that, though it may not solve your issue.

 

If it's an advertisement, would an ad blocker be an option for you? This works really well for me.

 

Cant use an ad-blocker for that, because watching the ad is the goal.
The issue is that it is too touchy and will install unwanted apps.

 

Go into the app info page for that game.
Look at the permissions, and disable the permission to install apps.

If it is not that, then check settings under accessibility and turn off accessibility for that game.

If none of that works, then try

Settings
Apps & notifications
See all
Overflow (3 dots upper right)
Show system

Now find this Instant Install.
Force stop it, then delete all data.
(storage, then go back one page)
Now disable it if you are allowed.
(uninstall if possible)
Now deny all permissions for it.

 

If nothing else works, are the ads opening with your browser, or from within the game?

If it's with the browser, then deny the permission to install apps for that browser.
(This is good practice anyway.)