Holding doors open, letting people with one item get in front of me, etc. are just "normal" behaviors for me, also.
As far as helping people in stopped cars - so many news stories have made me very very cautious. I'm more willing to stop for a semi-truck than a four-wheeler.
I also had an experience of -"don't judge the book by its cover"
We were being tourists in Key West, FL and I had looked through one of the public buildings - maybe the town hall - there were a lots of steps, anyway - and when I came out I saw this group of scruffy looking young people that looked like they were drinking beer - and was kind of dreading having to go through the group to get back to the sidewalk.
Much to my surprised, they offered to help me get down the steps and were very polite.
An occurrence that saddened me - I was at a nursing home garage sale, and I helped one of the residents find some slacks and borrowed a measuring tape to improve the odds of the pants fitting her. I spent a little bit of time talking with her - she said she was just waiting to die! - but she seemed so grateful for the short amount of time I spent paying attention to her.
One of my BIL's shocked me in a pleasant way - while my Mom was in the nursing home before she died, M started talking to this lady that was in a wheelchair in the hall - I didn't even think the woman could hear or speak - but she thanked M so much for talking to her. Now what makes this event unusual, is that M avoids family events like the plague and is not known for being sociable.