I need your help!!!

I have an 18 month old who self soothes, she gets put in her cot for naps & bed time & will fall asleep on her own.

However whenever I am out, if she falls asleep in the car for 10 mins I can’t get her back to sleep! Nor can I transfer her from car to cot. If I’m out & she falls asleep in the pram for half an hour that’s it, that’s her nap for the day.

No matter what I can’t rock her to sleep, I can’t seem to soothe her myself in any way!! It’s like her way or nothing. What am I suppose to do?...