The sunroof opens the closed car to the sky, so it stands for letting light and fresh air into a routine. Dream books read it as a wish for openness, inspiration or a little freedom on the daily road.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.