cpap noises

New to Cpap, trying to figure out all noises. I get that some of the sounds are from my own breathing or snoring amplified by the hose but sometimes in the early hours there is sputtering sound that seems to be from the Resmed S10. The machine is normally silent or softly purring. I have tried checking the connections on the rise, ensuring the humidifier is well watered and that the machine is on stable surface. It sounds like the machine motor is straining. What I am doing wrong?

Water/moisture in the hose?..Be sure the machine is lower than your mattress so any water can run downhill back to the humidifier.