Needs doctor’s advice. Though I experience that when sleeping at night and you don’t change your position and you wake up in the morning it surely happens. It’s just a freezing muscle as you don’t move your muscles becomes stiff. I do exercise shaking my head left to right and I change my sleeping position..each of us is different best really to see your doctor.

It happens to my face developing a masking face too stiff, so I get a chewing gum or mouth exercises and facial exercise by rubbing a moisturizing lotion and massage your face or drink water. It works, at first I thought I was experiencing stroke but when I take my meds I’m normal again. But if it doesn’t go away see your doctor immediately.
Again each afflicter differs from the rest.,that’s why you are advised to visit your doctor.

Since this is a sudden change, I would call the doctor. It doesn't sound normal.