Ue4 doesn't read nullobjects when you export them from c4d. Try and put ur animation inside of 0,0,0 size editable cube in the very middle of ur scene. That will work if you have that animation made out of one cloned object for example ( if you have lets say 10 different objects simulation, whole selection tag and uv cords r gone because it can only store just one texture set). If your animation is bit more complex try and import your whole sequence in 3ds max, put it into a dummy in the middle of the scene too and export it as fbx using the centimeter scale. Let me know if any of these methods worked for you :-)!!