Tai Chi movement is interesting and tai chi non-movement may be even more so, especially if you are trying to detect the difference between the two. One thing to look for is if a part of the body is not moving, then the part attached to it probably isn’t moving.
For example, sometimes a part, such as a shoulder, runs up against stuck ribs which don’t support the shoulder movement. The shoulder is moving in isolation from the rest of the body, throwing off one the first things a learner should understand: whole body moves as a single unit. You can think of this, and practice it, in terms of bio-mechanics or energy. Bones, joints, ligaments and tendons, or qi (yi-qi-li).
More often than not we don’t recognize this is happening, even though we have a frustrating sense of something not being right. Aggravating it is. It’s not that it’s not right, it’s just not moving.
Here is a little solution: track this non-movement to its origins. Become aware of what moves or not. Learn how to move any one of these parts. Repeating single basic moves rhythmically is great to loosen and move stuck spots. You usually have to change your idea of how to move. You have to see it in your mind’s eye before you are able to move what you haven’t moved probably in years. Look at the joints, ligaments, and tendons, not the muscles. Move them. Feel the energy flow through the body.
Check out this sample of George Xu doing Chen form here, followed by a nice explanation