Check her nostrils to see if there is any food/debris blocking them. Also look in her ears for any lice/mites or infection.
Have you added any new birds to your flock within the last 30days?
Sneezing if occasional can be normal clearing the nostrils of dust, food, etc. Shaking the head - could also be an adjustment of the crop - depends on what it looks like and how often. If she is continually doing this, a video of her actions would be helpful.