Well most people can not really handhold a 105mm lens at 1/60th. You may get lucky but usually not. Your example is not sharp and that may be due to a slight camera movement.
But there is a simple way to find out if its you or the camera. Just put the camera on a tripod and shoot a shot at 105mm at 1/60th, then shoot the same exact shot handheld. Now compare the two in PS and see if the one on the tripod is quite sharp, and the one handheld, less so.
However, be sure that you are really focusing correctly. Some people will focus on the eyes, for example, and then hold down the shutter to lock the focus, and then recompose the shot. At f4, this is almost certain, to mean you will no longer have the eyes in sharp focus. So, if that is what you were doing, you also have a possible answer. But in your tripod test, do not do the focus, lock, recompose method to be sure that that possible problem is eliminated.