Another user reported something similar a while back. Have a look at that thread.
What is your minimum pressure set at? It should display briefly on the machine when you turn it on each night. The minimum and maximum will be displayed in the top right. The current pressure which should initially be the ramp start pressure will show in the middle of the circle, if you are using the ramp. The reason I ask is that out of the box the machine will have a minimum of 4 cm. Some people, like me find that pressure too low and it feels kind of like suffocating. That said, you should feel that way each night on start up too, if the minimum pressure is too low. Something to discuss with your provider.
I use the same machine and also use some free software called SleepyHead. You can view your detailed machine data with this software including the actual pressure delivered during the night. It certainly would tell you what is going on with pressure. The detailed data of all your nights so far with the machine will be stored on the SD card, so it would be a matter of downloading and installing the software, then transferring the data from the SD card with a card reader to your computer. That would let you look back and see what happened to your pressure on the nights so far. Assuming it verifies what you are experiencing it would be good evidence to give your provider to get a new replacement machine.
One simple thing to check too is your power cord connections. This summer I had bought my wife a new power supply for her CPAP. It worked OK for about 4 nights and then it started to shut off in the middle of the night, many times causing symptoms like you report. It turned out to be a faulty plug on the new power supply. It was a molded connection and the wire or solder joint inside the plug must have been bad. If you wiggled it a certain way you could make the machine stop and start. I gave my supplier a copy of the SleepyHead report showing what it was doing, and they immediately sent me a new one.
Hope that helps some,
Unfotunately Sleepyhead only works on desktop/laptop computers and all I have is my phone.
There are a couple of other options. Your data is as portable as your SD card. If you can convince someone with a computer to install SleepyHead you could take your data to the computer. On the ResMed AirSense 10 AutoSet, the data is available wirelessly to your machine provider. They should have software similar to SleepyHead to look at your results.
I agree 100% with Sierra. During the first week (before I had Sleepyhead) I would check the operating pressure during the night. I found out that as soon as I was supposed to be asleep the pressure would run around 8 to 10. So I raised my minumum pressure to 9 and have been happy ever since. Trying to breath at 4 caused me to pull a vaccumn. Very unpleasant. Your life with CPAP is easier when you take control.