Three years later someone actually answered the questions. LOL
Welcome to Android Central.
6GB of RAM is a pretty good number but it may depend on what's going on in the background.
How predictable is this? It happens every time, once in a while, a few times a day? I'm asking because I'd like to know if you can cause this to happen?
Is it all games or only certain games? This would tell us if something like solitaire where nothing much is animated makes a difference vs something like PUBG where the processor is being put through it's paces.
Are you using Samsung's Game Launcher?
If it closes and you reopen it does it continue to close over and over if you try again or will it play after a time or two? Does this change if the phone restarts vs kicking you to the home screen?
Since this issue seems to revolve around games I'd like you try few things.
If you're using Samsung's Game Launcher (GL):
Before opening Game Launcher open your multi-tasking screen, some may call this the quick switch screen but basically the screen that shows all of your apps that are not closed and are being held in the background, and close all apps. When you open Game Launcher it will be the only thing shown on this screen. Now try to play a game. What is the result?
Just like before close all apps, open GL and select your game, whatever happens, it plays, the phone restarts or you get kicked to the home screen, go the multi-tasking screen again and close everything except the game you want including GL. I'm curious if GL is the problem.
Turn GL off and try your games. GL should be under Advanced Features, it's near the bottom of the list on my model.
I'm thinking the issue is either Game Launcher or Game Booster settings.
Let us know what you find and we'll go from there.