There are several reasons why a person may have upper back body pain while sleeping or waking up from sleep in the morning. Some very common ones are as follows:

Bad Sleeping Position Probably one of the things that most contribute to upper back pain while you sleep is your sleeping posture. When you sleep, the spine is supposed to be neutral, but most people end up unknowingly stressing the upper back by sleeping in positions that twist or contort the spine. Sleeping on your stomach, really thick or firm pillows, and sleeping with your arms overhead are all contributors to foot or ankle distress.

Mattress Problems: Either a lack of support, a sagging mattress, or one that is too hard can be to blame for upper back pain during sleep. Any mattress that is not comfortable and supportive of the natural curvatures of the spine can be a reason to strain the muscles and inflame the muscle tissue of the upper back.

Strained Muscle or Injury A strained muscle can be caused by abrupt movements, heavy lifting, or any form of physical action that can directly affect the upper back. If this is not diagnosed and properly cared for, sleeping in the wrong position may exacerbate the conditions of one of the affected or inflamed muscles.

Underlying Medical Conditions Sometimes upper back pain while sleeping could be an indication of an underlying medical condition like arthritis, herniated disc, or even referred pain arising due to problems in other areas of the body like the neck or lower back. Some systemic conditions or chronic conditions, such as fibromyalgia or spinal stenosis, might also cause constant upper back pain, including while lying down.

Stress and Strain Too much physical and mental stress can lead to the overworking of muscles in the upper back and shoulder areas, thereby leading to pain that increases in intensity during resting hours, including sleep. 

     To avoid or minimize upper back pain while sleeping, the following steps may be taken:

Sleep in the right position: Sleep on your back or side, with your pillow supporting your spine. Do not sleep on your stomach, as it rotates your neck and upper back.

Choose the right mattress: Go for a mattress that will give firm support and effectively conform to your body's curves. Often, it can be advisable to choose memory foam or hybrid mattresses to utilize pressure relief and spine alignment techniques. 

Use ergonomic pillows: Besides the mattress, the right pillow can make a big difference. Look for pillows that offer ample support for the neck and shoulders to keep the upper back in a neutral position.

Engage in good lifestyle practices: Regular physical activity, proper day posture, and stress relaxation methods all serve in the reduction of muscle tightness and stress in the upper back, which is exacerbated at night.

Underlying Medical Problems: If there is an underlying medical cause due to which the upper back pain occurs, this condition must be diagnosed and treated thoroughly by a professional healthcare provider.

     Now that we have gone over the common causes, let's dive into mattress features that can help with upper back pain. 

Firmness Level: The general recommendation by experts for upper back pain is a medium-firm to firm mattress—this will provide enough support to keep proper spinal alignment without being too hard and causing pressure points. Side sleepers may need a slightly softer surface to cushion their shoulders.

Pressure Relief: Acquire a Mattress that produces pressure-relieving functions from elements such as memory foam, latex, or specialized comfort layers. These contours with the curve in your body and distribute weight across your body, hence easing tension from your upper back.

Zoned Support: Some mattresses consist of zones at a varied firmness so that personalized support is truly given where one needs it. They generally have firmer center portions to keep your spine aligned and softer cushioning on the shoulders and hips.

Contouring Ability: A mattress that conforms to your shape, especially at the height of your upper back, keeps your spine in a healthy position while reducing pressure points. 

Edge Support: The human spine is designed to flex in many different directions but not to twist. A good disabled edge support would avoid the situation wherein rolling off the side of the bed contextually twists your spine.

Memory Foam: This pressure-relieving material boasts one of its wonderful properties, including being able to contour according to the natural curves of the body and providing needed comfort at pressure points. It is also very good for side sleepers who have upper back pain.

Innerspring: Most traditional innerspring mattresses will be on the firmer side, which may be helpful when dealing with many upper back problems. Pocketed coils will allow much more contour and much better motion isolation for people with upper back issues.

Hybrid: These are designed to join the support of the innerspring with pressure relief from the foam layers of comfort. This could be the best compromise for upper back pain.

Latex: The natural latex is incredibly responsive to pressure, and the pressure-relieving properties let it cushion the upper back without ever feeling entrapped.

     Ultimately, the right mattress for upper back pain is an extremely individual one. Begin by accounting for your sleeping position, your body type, and any prevailing conditions or injuries. It may take some trial and error to nail down the perfect fit, but the quality-of-sleep improvement and pain decrease will make it well worth the effort.

     If one does suffer from upper back pain while sleeping, then certainly there are some remedies and treatments that might alleviate this:

Over-the-Counter Pain Medicine NSAIDs such as ibuprofen and naproxen help in reducing the inflammation and thereby relieve pain in the region of the upper back.

Heat or Cold Application A heating pad, a warm compress, or even an ice pack applied to the area where the spasm has occurred might go a long way in soothing the muscle spasm and discomfort.

Massage and Stretching Gentle massaging of the upper back and some light stretches or exercises to the area are essential for improving blood supply and flexibility.

Physical Therapy A physical therapist can apply specific treatments and exercises focused on improving mobility depending on what is at the root.

Chiropractic Care Chiropractors, with their spinal adjustments and other manual therapies, can help in the realignment of the upper back and bring relief from this condition.