Nocturnal bowel mevements.

Question
My 13 year old spayed female German Shepherd has been having bowel movements in her bed, at night.  Nothing unusual in her normal stool.  No recent changes in her feeding or overall lifestyle. The movements occur between midnight & 3:00 AM. We feed 2 cups of kibble at morning & 1 cup of kibble at evening. Additional exercise after evening meal doesn't promote a bowel movement.

Answer
Your dog is getting very old. 13 years old is quite old for any dog and dogs, like people can have fecal incontinence.

Usually this is not a feeding problem so much as it is a nerve conduction problem. She should see the vet and have him test her reflexes etc in her back legs. That will give him an idea of what could be going on with her nervous system and her spine.  

Sometimes these dogs have issues with walking or getting up in the morning. Some don't and the problem is more subtle than that.

In either case, any dog that is have incontinence issues should see the vet. Sometimes there are things that can be done with steroids, vitamins, etc.

Call the vet and make her an appointment.