“There is no stressor, but the body is flooded with a sense that it needs to do something.”

Anxiety appears to be more prevalent at night. Everyone has anxiety at some point in their lives, but it becomes a problem when excessive fear and worry last longer than one stressful incident. It will begin to appear for months at a time, disrupting daily activities such as work, relationships, responsibilities, and, of course, sleep.
Sources: Scully, S. M. (2020, June 26). Tools and Tricks to Calm Your Anxiety and (Finally) Get Some Sleep. Healthline. https://www.healthline.com/health/mental-health/tools-and-tricks-to-calm-your-anxiety-and-actually-get-some-sleep#headspace