Here are some examples of when it's grammatically correct and natural:
* For example, ...
* For all intents and purposes, ...
* For the sake of clarity, ...
* For years, they lived in that house.
However, there are some cases where it might sound awkward or unclear:
* For I am the king. (This sounds very formal and old-fashioned.)
* For going to the store, I need my car. (This is grammatically correct, but sounds awkward. You could rephrase it as: "To go to the store, I need my car.")
In summary:
* It's generally okay to start a sentence with "for" in most cases.
* Be mindful of the context and how it sounds. Sometimes, rephrasing might make the sentence more natural.