What Causes Stiff Neck, Shoulders, Arms, Thighs And Back In The Mornings?

I have suffered with neck,shoulder,arms,thighs and back for the last 18 months. I get very stiff if I sit for a long time such as long car trips I seems to freeze up. I find the morning is the worst as I am so stiff in joints until I get under a hot shower. By late afternoon I come good and seem to be relieved of a little of the pain