Your problem can be related to Muscular Spasm.Due to lack of exercise ,your back muscles are weak and whilee in same posture
during sleep there is no movement for long,these muscle go into spasm.and hence you feel pain.After some
movement these spasmed
muscles becomes somebut mobile
and hence pain
RHUS TOX 30 ( Dr Reckeweg) Drink 5 drops in 1 poon fresh water 3 time daily
Start doing morning exercises daily for 20-30 minutes.