Hi,
This seems to be in continuation for a long time. 1st is to rule out any kind of nasal blockage due to nay reasons and then to look further airway, probably (laryngomalacia). If your child is comfortable when he is sleeping on his chest and stomach then he might be feeling better but if lying back and having problems then it can be the issue I mentioned. But need to have more discussion and then reach a diagnosis
Next Steps
Consultant a pediatrician 1st video or live anything and then can be planned for evaluation and management.
Health Tips
Try to make the child sleep on chest and stomach touching bed (probe) position and observe.