Here are some examples:
* Then she walked out of the room.
* Then he decided to try again.
* Then we'll know the answer.
However, it's important to note:
* Context is key: While grammatically correct, starting a sentence with "then" might sound awkward or repetitive in some contexts.
* Alternatives: Often, there are more elegant ways to express the same idea without using "then" at the beginning of a sentence. For example, you could use a conjunction like "after that" or "subsequently."
Overall, don't be afraid to use "then" at the beginning of a sentence if it fits the context and sounds natural to you.