Is this a good time to talk?
This puts the other person on notice that something important is up for discussion. If they say it’s not a good time, please don’t push. They might be crabby, hungry, tired, or simply not in a receptive or productive frame of mind at that moment. Which means the conversation is not likely to go well anyway.
So hold your tongue, and ask them when would be a better time. If you were burning to talk right then and are worried you’ll forget what you wanted to say, jot it down and save it for later.