Does anyone use the maxi-Cosi pebble plus car seat? Recently my 4 and a half month little boy has…

Does anyone use the maxi-Cosi pebble plus car seat? Recently my 4 and a half month little boy has been screaming his head off when we put him in it. He was absolutely fine before and nodded off to sleep straight away in a car. He only screams when the car is moving. He is fine when the car stops or when the seat is attached on his buggy. I also took out the newborn insert but that hasn’t helped either. Any advice would be very helpful.