My oldest son starting skipping naps like this at that age. It would last a week or two, then he'd start taking them again. That happened off an on for years- until he was 3.5 years old and stopped quiet time all together. What I did was I still made him sit in his crib and cry for an hour, or play for an hour- his choice. He had crib toys, books, and stuffed animals he could play with. I would stick through it and keep giving him the quiet time (or, not so quiet time if he makes it that way and crys) as he obviously needs it because he is cranky or sleeping in the car. Maybe try to wear him out more before nap time- run around a lot right before hand or do some other activity that exerts a lot of energy. Or, I don't know what your naptime routine is, but maybe do some more quiet time activity than normal. For instance, if you read one book to him, maybe read 2 or 3 books to help him wind down and become drowsy enough that he will nap. I hope this helps.