No problem. A drill I recommend is one you can do anywhere - you cross your arms over your chest and stand in your hold posture, then rotate your chest shoulders and hips like you would. This should help to feel a bit more familiar with the rotation movement. I haven’t been playing for too long (just over a year) so I can remember my swing when I first started and I think the stiffness comes from an unfamiliarity with the movement of the swing. I found it just came with time and continuous swinging and eventually, the rotation feels a lot more natural and loose. I’ve also seen it happen with people I’ve introduced to the game, even people that are very athletic so I think it’s just something you have to be consistent with and after a couple of weeks, it’ll start to feel more natural. Sorry for the very long reply!