Don't be concerned about it, some cars the flued wobbles a lot do to that does not have a fast flow, also sometimes it depens on the colant mixutre, if it is old and or high water mixture it will do that as well. And also as lars said, that why there is the seppart cooling fan as well, another option is your clutch on your fan could be bad. just keep an eye on it. But symtems like that a bad clutch could case that. (Clutch on the fan)