unity – Unity3d Prevent velocity from being increased by fixed joints

I am currently working on a Unity3d project that makes use of fixed joints. When connecting two GameObjects using a fixed joint, I noticed a behavior where the gameobject that becomes part of a fixed joint gets velocity added for a short time. The added velocity disappears after a fraction of a second.

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I add the fixed joint as follows:

baseObject.AddComponent<FixedJoint>().connectedBody = targetObject.transform.GetComponent<Rigidbody>();

Is there an explanation for this behavior and is it possible to prevent it?