* The question is incomplete: It should specify what letters the words need to start with.
* It's a wordplay trick: The "starting with" part is meant to make you think about the beginning of words, but the answer actually lies in the *end* of the words.
Here's a possible solution:
If the sentence needs to have all words ending in "ing," we can use:
"Something is happening."
Let me know if you had different letters in mind!