Unless: 😂 It’s a good joke 😂 and you are good at telling jokes. Therefore, for most of us: no jokes. There is another serious reason not to start with a joke. The primacy-recency effect means your audience are more likely to remember the beginning and end of your presentation than the important bit in the middle. Do you want them to remember your joke or your message? Instead of a joke, therefore, I suggest you start your presentation with a promise.