Our dreams are about us, not the people in them. We think them up to help ourselves.

Cars are a symbol of how we "move ourselves" through life/society. That you were a passenger (instead of driving) may mean that you are allowing your "crazy" thoughts or emotions to direct you instead of taking control yourself. That it was your mother kind of makes me think it might have to do with your health/welfare? Are you taking good care of yourself? Mothering yourself well or do you have issues there?

Being in your childhood home could indicate that you have an issue stemming from that period of your childhood that you are still struggling with? Interesting, in my shower they're all safety/women's razors that wouldn't slash very well? Interesting too that you could "barely react". You're not quite taking a "back seat" in the car to your issues (but are a "passenger" rather than driver) but here you are perhaps saying that in your childhood you "barely reacted" to obvious emergencies/strong feelings/behavior?

I am guess you helped take care of your mother, emotionally, as a child because of her depression, instead of her taking care of you. I would think there's some unconscious understanding that that is not healthy for your growth, that you need to take care of yourself better. I think the actions of your mother in the dream were so bizarre and extreme to get your message (whatever it may be) across to you, it's an "emergency" that you learn to take care of yourself and not "barely react" anymore.

I don't know if you learned your mom's depression or are perhaps anxious? But I think it might be hard for you to act in your own best interests, put yourself and your life first (only life you get).