I started occasionally having this problem earlier this week.
I have found a solution that might help other people. Usually I use the electric shutter and by selecting in the menu mechanical shutter, the problem is solved
You have to give some more information.
When does it happen? Always? or when you turn on your camera? Is it only solved by setting the mechanical shutter? Or also by turning the camera off and then on again?
Everything you do or how it happens helps solve your problem.
I only use the mechanical shutter. Only when I make video's the electronic shutter used.