This is an obvious answer. When the body is under stress or when you feel nervous the amygdala which is part of your brain that controls your emotions, gets larger and takes over the controls. Then, the hippocampus, which is involved in the formation on new memories and is also associated with learning, temporarily narrows. Eventually, it blocks the process of recalling information and your brain isn’t able to find the words or main points that you need to express in your presentation. Therefore, you need to stay as calm as possible during those blank mind moments and continue trying to remember your ideas and points that you need to express during your presentation.

When I say repeat, it doesn’t mean that you need to repeat a particular point over and over, however you do need to repeat your main points at least 3 times. The repetition of your main points can be paraphrased but it is important to use the magic number of 3 in order that your audience remembers the main points of your presentation.

It is important to smile during your presentation, by giving a smile to your audiences it builds a genuine connection and creates allies within your audience. This will enable you to build confidence and overcome any awkwardness during your blank mind moments.
So in summary, stay as calm as possible during your presentation , I know it is easier said than done, but keeping this main point in mind will help you. Secondly repeat your main points 3 times throughout your presentation and finally smile and show warmth to your audience throughout your presentation.