Agree with possibly having the eyes and hearing checked and possibly thyroid.
I would wonder if something is going on outside the house when you aren't there. Anyone workmen, utility people, new kids on the block, new dog(s) near by, etc? Postal person coming a different time of day? Trash trucks coming a different time? Anyone close by get a new MC? Yes, that can even do it.
Thank you for your advice...I will have her checked out next week. We take them for their regular check-ups but I think I will take her just to be safe. Hope its not too expensive for the test to be done.
Have her sight and/or hearing checked.
The fact that she was startled tells me that one of her senses may not be as sharp as it used to be, and the reason she goes to her crate when you all are leaving the house is because she feels safe there when she knows she's alone in the house. Something may have scared her while you were not at home and that is her way of dealing with it. In the meantime, the reason she is so happy and full of energy when she goes on her walks with you is because you're there and she is happy because her little world is complete. Seven is not old but it IS working toward middle aged doghood, so it's entirely possible for her to be showing some signs of her advancing age.
Ghilly