Hi Margaret, that shouldn't happen. Which of the following seems to be the situation:

(1) Default Search Engine setting is changing from your last setting. See the steps in the following article to find and adjust that setting:

Manage Firefox search settings

Do you notice that changing in response to a specific event, such as:

• every time you quit and restart Firefox
• every time you shut down and restart Windows
• some other timing

(2) Default Search Engine setting is fine, but when clicking in the address bar to enter a new query, the little widget at the left end changes to a different search engine while you are typing.

(3) The address bar looks normal, the drop-down says Firefox will use DDG, but the results appear on a different site.

(4) Some other strange chain of events.

(1) I have my default search engine set to Duck Duck Go. Every now and then it changes, and I usually don't notice until I don't get the results I want. Often it's changed to eBay or Wikipedia or some other constrained environment. Then I go look at the Firefox settings and the default has changed there.

I go in and out of Firefox a lot. I don't shut down and restart Windows very often, and it definitely happens more often.

I can't identify any specific situation, so it's "some other timing."