Sometimes I can visualize a pose in my head and sketch it out. Other time I struggle with it. Then there are times where the pelvis or leg (started off as circle / loose cylinder) dictates the rest and everything just flows out smoothly without much thinking. I believe the reason for my struggle is not drawing enough different poses from references.
Quickly capturing a pose from a photo is a useful skill to have when you can’t think of an interesting pose [or] you have a hard time visualizing it in your head. I believe that the more you copy poses from photos, the more your mind will grow in this area, which will later help you to draw a variety of poses from imagination… that muscle memory will kick in.