I almost all movies where you could see an animation about an asteroid, they move in a very distinct way.

I don't know how to explain better, but I think what we can see in the movies is that the asteroid is rotating around the x axis with constant speed, around the y axis with constant speed and around the z axis with constant speed, where x, y and z axes are of a reference frame.

What is this kind of motion? Is it correct?

According to the Euler's rotation theorem any 3D rotation that has a fixed point also has a fixed axis. So if they are rotating around more then one axis, does it mean that they don't have any fixed point? But then what is the motion what their center of mass is doing?

I would suppose, that the correct movement would be when asteroids are rotating like planets, around one fixed axis. But to me the rotation commonly used is not like that. What is the correct way?