It depends on one's Kamma apparently. They don't actually state in the scriptures that I have read what actually happens, but they state what is important to think before it happens. It's important to have resolved past regrets, fears, worries, and such because if they arise in the moment of death, then that can ignite that particular Kamma and influence the next moment, which is often birth consciousness. So, it is quite important to resolve past regrets about one's past actions. It's also very important to direct the mind towards a beneficial object in the mind, your meditation subject if you have one. My favorite is reflection on the Buddha. Some people like Compassion/Lovingkindness, one teacher recommended reflection on one's good Kamma, so one's good Kamma fruits. I have read some theories about what happens and what one is supposed to visualize and think, but that was very confusing. Very difficult to remember these things unless you have practiced them.