Can you use or to start a sentence?

Yes, you can use "or" to start a sentence. It's not grammatically incorrect, although it can sound a bit informal or conversational. Here are some examples:

* Or, you could try this other approach.

* Or, maybe we should just start over.

* Or, if you prefer, we can discuss it later.

Using "or" at the beginning of a sentence can be effective when you want to:

* Introduce an alternative.

* Continue a list of options.

* Emphasize a contrast.

Just remember that it's generally considered more formal to start a sentence with a different word or phrase.