How do you find the cheapest flight when you don't care about when you go?

I tried searching through this sub, but couldn't find anything that addresses my particular issue.

Basically, I want to plan a trip to Germany sometime in the fall/winter, but I don't really care when it is that I go.

I want the trip to be around a week, but again, i'm open to a couple days shorter or longer depending on what I can get for the cheapest.

Is there any sort of way to search for flights in the sense of, "I want to book a weekish long trip to Germany anytime between September 1st and December 31st."

For this kind of scenario, would it beneficial to hire a travel agent to find one for me?

Any tips or advice would be appreciated! Thanks!