What can cause sudden constipation?

Many Issues Interact: Emotions, too sedentary, dehydration, too little fiber, etc. Etc. & in combination. Intestinal muscle motion totally under nervous system control (subconscious) 24/7. Thus 1 of biggest drivers of intestinal changes is emotions expressed into intestines, e.g. “nerves”/nausea before test as child/teen. Internal control dominant. Being very physically active tends to dramatically ↓↓ constipation.