My son was 2 yrs old when he had a near death experience like you often hear about. He didn't verbalize it until he was 4 yrs. old. He had miocarditis, a virus that landed on the heart, which can simply be remedied with an anti-biotic but back then the local hospital was clueless. He was near death when he was flown by helicopter to Children's Hospital in DC. They misplaced the test results, implanted a pacemaker, and then found the test results 2 weeks later. His heart started and stopped multiple times during the whole event, lost fluids, etc.
At age 4, we took a trip to Tucson Arizona. He pointed to the top of the mountain and said to my sister, "I've been up there with God". I asked him what God looked like. He said, "I don't know because he was standing next to me but I know he was bright and white and we were looking down from the top of the mountain". What did you see down below? "Nothing but darkness". I asked him to draw a picture but I couldn't make anything of it. I like to think the darkness he saw was because he was coming back to life and there was nothing more there to experience.
When he started school he came home and told me "I know what it's like not to exist". This really surprised me because he was only about 7 yrs old and here he was talking about his existence. I asked questions of course. He said "I can make myself not exist at anytime or anywhere and I can even do it now but I don't want to because I don't like it." He never talked about it again but it did subside eventually. He's 29 now. He has some issues linked the the trauma experienced at such a young age.