In what way can a body begin to move in the absence of interaction with other bodies (for example, in open space)?

In order for a body to start moving without interacting with other bodies, it is necessary that a part of the body be separated from it at a certain speed.
According to the law of conservation of momentum, another part of the body will move in the opposite direction with the same momentum.
The momentum of the body P is the product of the body’s mass m by the speed of its movement V: P = m * V.
An example of such a movement is the rocket’s jet propulsion in space (weightlessness).
The burnt fuel is separated from the rockets at a certain speed in one direction, and the rocket starts moving in the opposite direction with the same momentum.