Why the obstacles goes fly?

Hello, everyone. I start the game developing with unity. I’m following a tutorial from a youtube channel called “Brackeys”. In episode 6 he created obstacles prefabs and I did either, but when I started the game most of them are flying(especially which are near to each other). What’s the solution to this problem?

The red ones are flying when I start the game.

Are they positioned on the Floor in the first place?
Do they have rigid bodies on them… If yes for what reason? This might be why.
If they are just GameObjects / Cube Meshes than they should stay where they were placed.

@NightmaresDev
When I remove Rigidbody component it worked, but in now, when the player collision with the obstacles which I represent with red shapes it isn’t stopped. But if the player collision with one of the red shapes before the crash to the same type(I mean the prefabs which are near to each other), it’s working.

And in the video, I guess, he added rigidbody component for mass properties. (Because he just worked with mass properties in rigidbody component)