I have had recurring lower back pain for about 2weeks. I initially experienced it when I slept in a bed away from home so assumed it was just the bed. However, since then, the symptoms have continued, initially fairly constant so took Advil and applied heat....with some relief. However, the discomfort does not feel like the typical muscle spasms I have experienced in the past.  At times, it seems more pronounced on the left side.  At times, it disappears all together.  But it recurs at nite after I have bee sleeping for a few hours and it is difficult to find a comfortable position.  Abdominal discomfort accompanies it at times as does a boating feeling. I also feel more tired than usual.
Hi and welcome to ChatDoctorBased on the description of symptoms, I think it is Postural back pain owing to the odd position adopted while sleeping. Any muscle in the body will tend to go into spasm (tightness) if it is held in one particular position for a given period of time. So, I suggest you to avoid sleeping positions which produces pain. As you rightly said, hot shower always helps as the heat produces relaxation in the muscles. If your pain is intolerable, use oral muscle relaxants and massage painkiller creams over the affected regions. An MRI scan may be needed to rule out any underlying pathology that is producing pain. I do hope that you have found something helpful and informative, and I will be glad to answer any further query. Take care.