Doing a hard shift when I climb up hills and sometimes down hill on 2011 Mercedes-Benz E350

It sometimes happens on a road with a long gradual downhill, and I'm going about 3rd gear. It's been happening regularly also when I come up my road, which is a long uphill--not super steep, but an uphill climb. It will shift very hard and abruptly to the point of startling me.

Asked by for the 2011 Mercedes-Benz E350