Hmm i know some babies tend to hate cars (personally never had this). As long as my girl is fed and had some time to move around she will knock out in the car seat. Does she look comfortable? (Head support, straps with guards etc) Put the shade up to make it darker Can get a portable white noise machine Make sure shes fed and tired before you leave. Turn music up louddd like louder than youd want lol We drove 20 hours to Florida with our 4 month old and 3 year old and this all worked well for us! Good luck!
Have you tried infant chiropractic work? Some babies hold more tension in their bodies than others from the womb and birth, and the car seats can make it more uncomfortable for them.
My daughter is the same way. It just started like a month ago. She does go to the chiropractor regularly, the seat fits, shes fed, all the factors are there.
@Lexe has anything helped at all?
My sister cried for years in the car. Turns out she gets super carsick. Shes 15 now and still gets carsick. Nothing helped but time… and forward facing her carseat as soon as was mostly safe for her.