Why does my rigidbody(2D) accelerate?

I'm working on a 2d game where my player is intended to move along the x-axis with a constant velocity/speed. Despite setting the velocity of my rigidbody to a value, the rigidbody does accelerate.
(note: the ground has got a friction of zero)

Code (CSharp):

1. void Start () {
2.  
3.         Physics2D.gravity = new Vector2(0, -9.81f*5);
4.         rigidbody2D.velocity = new Vector2 (0.05f, rigidbody2D.velocity.y);
5.         Debug.Log (rigidbody2D.velocity.x);
6.      
7.     }

Has anybody got an idea why it does that ?

 

Thanks for your reply. The issue was that my character was a child of my camera, therefore when my character moved and the camera followed him (The camera has its own script), the offset of the camera was also applied to the character.