I have the same year car. All of these manual transmissions for this year apparently do this.

I have found two things that help.

1. The most effective way is to downshift into first gear just before you stop. Then you can take it out of gear if you want and release the clutch while you wait. When you are ready to go, just put it in first and go. It has never popped out of gear when I have done this.

2. When I have forgotten to do the above, I double clutch the transmission. In other words, before I put it in gear to take off, I push the clutch in twice. Then I push the clutch in, put it into gear, and off I go. It has slipped out of gear two times using this method, but it works almost as well as the first option.