It is not advisable to DM someone who you have not interacted with before after only 30 minutes. It is best to wait for a bit longer, at least 1-2 hours, before sending a DM. This allows for a more natural conversation to develop and gives the other person time to respond. If you do decide to DM someone after only 30 minutes, make sure to introduce yourself and explain why you are messaging them. This will help to create a more positive and friendly interaction.