Is it normal that first run of build upload every asset to memory?


I found the very serious problem with running the build of my game. Exactly… first game start takes ages. At the second run, it starts almost instantly, but when I copy the folder with the build to another location situation is the same. I used Process Monitor to look what is going on and it looks like every game assets are loading to memory at the first run.

If it is important… This game is 2d Platformer with a lot of sprite assets. Is it necessary for Unreal to behave like this?
It there some option to avoid it?
Maybe this is not the real cause of my problem…?
Please, any help will be apprised.