What Causes Stiffness Of The Palm When Sleeping?

I am a relatively healthy female in late thirties and I have recently woken up with a stiff left palm when I bend my pinky and ring fingers down. The palm kind of locks momentarily and then the two fingers pop back up. My fingers are all flexible and as the day goes on it lessens or goes away but comes back while I sleep. I have chronic pain syndrome and I often have aches and pains and muscle twitching all over including in my fingers. I sometimes experience mild symptons of having a pinch nerve in my arm or hand.