crying in car seat

Avalon
FTM. My LO is 7 weeks and cries when I put him in the car seat and while driving he cries till he over heats and I feel as though he will pass out. 
When he was newborn-5 weeks he didn't cry while driving but he did cry once I placed him in the car seat. 
All of a sudden something changed. Has anyone else experienced this? Any tips?