What could be causing upper back popping?

I have a lot of “popping” going on in my upper back, especially when I sleep, turn over, and when I first get up. What could be causing this?

Why Does My Back Crack So Much When I Twist?

Upper Back Spasms: Treatment and Prevention Tips

Back Acne (“Bacne”): Symptoms, Causes & Treatment

Back pain, Causes, exercises, treatments

Lower Left Back Pain: 9 Causes and Treatment Options

Can Cracking Your Back Cause Back Pain?

Shoulder Clicking and Popping: Labrum Tear or Poor Scapular Position?

11 Signs Your Upper Back Pain Is Serious Trouble It May Be Your Desk Job - NJ's Top Orthopedic Spine & Pain Management Center

Shoulder Popping When Rotating? What's Normal (And What's Not)

Back pain and fever: Should I be worried?

4 Ways to Crack Your Upper Back - wikiHow