My baby did that in the hospital on our second night due to excessive crying. We panicked and called in the nurse and she taught us to turn the baby to the side to relieve the choking. Anyway she is 2 months old now and still choke her own saliva when she cries excessively but we are more calm now 😄
hope this helps https://sg.theasianparent.com/baby-choking-parents-guide