Maybe galaxy store is downloading some/suggested apps. check it out. I would suggest you to keep all automatic app updates to off. but you should check and update whichever app you want so that you can manage your data.
Please perform the following step to resolve the issue:
> Disable the auto update in play store (Launch the play store>>tap on left corner 3 bars>>Settings>>auto update apps>>turn off it).
> Run the device in safe mode and check the issue.
For further assistance, register your concern in Samsung members app (Open Samsung members app>click on “+“icon>send feedback>Error report/ Ask Questions).
