I was about 4 or 5 years old at the time. I was particularly annoyed because I was stuck in one of those car seats for children that strapped me down. This was bad because my back itched and I couldn't move enough to scratch it. It was a common theme with those car rides and I remember hating that seat as a result. My identity/personality was not the same then as it is now. My identity now only spans back a bit over 2 years.
Perhaps you were able to remember this incident because it caused you some discomfort or pain. Being in an uncomfortable situation that was out of your control probably made this stick out in your memory. It is interesting that your identity is so new and I wonder what makes you feel this way.