I have a 6WO who will contact nap during the day on parents who are awake & alert. Baby sleeps in the ‘kangaroo’ sleep position, skin to skin on our chest. Because baby is sleeping on their stomach, are there any risks of rebreathing? Head is always to the side but against parents body. And is there anything that can be done for babies who fall asleep in car seat with head to the side but close to the car seat cushion? When in moving car, not stationary. Thank you in advance.

Red Nose has the following information about why back sleeping position is safest
Always place baby on back for sleep

“Placing baby on their back to sleep helps keep their airway clear and ensures their protective reflexes work. Back sleeping reduces the risk of suffocation, overheating and choking.”
https://rednose.org.au/article/red-nose-six-safe-sleep-recommendations
https://rednose.org.au/article/why-back-to-sleep-is-the-safest-position-for-your-baby

Red Nose also has the following information.
“Sleeping an infant prone on the parent’s chest, especially skin to skin, is an excellent strategy for settling an infant when the parent or another adult caregiver is awake and able to monitor the baby. But if a parent falls asleep with an infant prone on the parent’s chest and unobserved the risks include prone positioning of the infant, and obstruction of the infant’s airway which can become obstructed by clothing, by the parent’s body or breast, or by the infant becoming positioned with his/her chin to chest.”

https://rednose.org.au/article/sharing-a-sleep-surface-with-a-baby

Where does your baby sleep at night?

And is there anything that can be done for babies who fall asleep in car seat with head to the side but close to the car seat cushion? When in moving car, not stationary.

Car Travel
Red Nose has no specific recommendations for time frames when travelling with baby in a car safety device - risk is related to how long baby is in that position. See the following information.
“Once the car journey is over it is very important that you remove baby from the car seat or capsule, even if this means waking baby, because it is not safe for baby to spend long periods in car seats, capsules or infant seats.

Research has shown that:

babies left in a sitting position for a long period of time may be placed at increased risk for sudden infant death.
car or baby seats may cause baby’s neck to flex forward which may block baby’s airway not allowing airflow
falls from car seats used outside of the car as infant carriers are common, often involve children unbuckled in their car seats and represent a significant source of head injury for baby. Never leave baby in carriers on shopping carts, counters, or other high locations “
https://rednose.org.au/article/are-there-recommendations-for-car-seat-or-baby-seat-use