Simulations that do not settle are pretty common. A few things to check:

1 -is there enough space inside the jacket? Most common beginner's fault is they do not yet appreciate the importance of room or 'ease'. Take a jacket that fits you well over a shirt. Measure the circumference of the sleeve and compare with the circumference of your arm at the same location. This gives an idea of the space needed. Do same for circumference of chest.

2 - are all normals pointing the right way (to outside)? If the shirt is folded there are vertices with facets pointing inside that push your jacket verts the wrong way.

Typical approach for layered garments: drape and freeze layer by layer, starting from the body. Make layers not yet processed inactive and invisible.