That's a good question for a new contributor! Let me try to give you an answer.
When you pour the coffee you give the body of coffee a rotation (clockward) in the cup. You can put a velocity vector field on the surface of the coffee. Initially, all these vectors have the same magnitude and directions parallel to the tangent vector on the side of the cup.
So in the middle of the cup, the rotation velocity has the highest value, simply because there is the least distance to travel before a complete rotation is completed.
The bubble goes along with this rotation (also clockward; just try pouring the coffee in the opposite direction; it would be very strange if this wasn't the case!). When the bubble is exactly in the middle (as well as the middle point of the rotation) it should stay there and will rotate along with the coffee (though in the video it doesn't seem the middle of the coffee surface has the highest rotation velocity, but let's assume the highest rotations velocities find themselves around the middle). The surface, in this case, must be symmetrical wrt the middle point of the round glass. The water molecules whirling around the vertical axis going through the middle point don't form a vortex.
But this is theoretically. Just a tiny displacement from the center is enough to let the effect occur, and this will surely happen after pouring. So in reality, when the bubble moves outward a bit, its angular velocity is diminished because of the interaction with the different (smaller) angular velocities of the coffee surface and because the angular momentum has to be conserved. This also drives the bubble back to the middle. You will never see the bubble moving too much away from the center of rotation. All angular velocities are reduced because of friction, tending to make all angular velocities equal. The bubble is doing a rotation dance!
Finally, the (angular) velocities all tend to zero because of friction and the effect is gone, obviously.
You made a great video. The temperature has to do with it insofar the viscosity of coffee becomes less if the temperature is increased. Maybe you can try to put the bubble in the middle and see what happens when trying to let the coffee rotate in such a way that the center of rotation will find itself in the middle, though this is very difficult to do!
The bubble spends more time in the middle when the temperature is higher (where it spins faster) because it's easier pulled to it than driven away from it. Obviously. Why? Maybe you can think about that for yourself (viscosity).
Here is another, new video.