To turn off this behavior call GEOptions.setFadeInOutEnabled(). e.g.
ge.getOptions().setFadeInOutEnabled(false);
See: https://developers.google.com/earth/documentation/options#new_feature_animation
Edit
The way you are adding and removing the placemarks smells a bit funky.
"Every time I delete the old placemark and add the new one I get this animation"
A much better way to do what you want is not to delete and add placemarks - it is to update the label on a single placemark.
In your example you need to simply call placemark.setName(whatever)
every second.
All the other code only needs be called once to initialize/configure the placemark.