Hi,
First of all, add Rigidbody2D components only to objects that have a Collider2D and that are supposed to be moved.
If a tree flies away despite not having any Rigidbody2D attached or any script that moves it, it might be that other game objects are moving relatively to it. Some people add a Rigidbody2D to the ground. When they start the game, everything looks as if it started to move upwards but, actually, it’s just the ground falling down.
If you want to prevent the car to be affected by gravity, you could disable the gravity for the car or, if you want to disable the gravity in general in your game, you could set the gravity to 0 in the physics2D settings in Unity.
Also bear in mind that colliders push other colliders. If your car is inside another collider, that might explain your car moving to the side.
Since I do not know anything about your project except for a vague description, this is just a guess, though.
See also:
- Forum User Guides : How to mark a topic as solved