Is this potentially what I'm going to experience after my first night with CPAP?

Two days ago, I had one of my worst nights ever. As I lay on my right side, still awake, I felt total collapse in my throat and I couldn't breathe. Switched to the usual left, and it was just as bad. My whole body felt tense and like I needed to stretch, I couldn't achieve a good sleeping position. I was trying to achieve a good position from 2 AM to 5 AM, in that usual could-be-asleep-but-am-awake-state, before I found the energy to just give up and try something radical.

I decided I was going to sleep sitting up, so I stacked a bunch of pillows and cushions on my couch and tried to get them to keep me upright. Somehow, miraculously, I achieved a very comfortable sleeping position and my throat was open. Best of all, somehow, I got my arms to hang off the couch and onto a rest behind it, in a very comfortable position.

I slept like a prince from 6 AM to 10 AM, and when I woke up, my muscles felt so relaxed I felt like a new person. I've had bloating for years, and I also felt like my stomach, in some weird way, "was finally allowed to bloat". My bloat remained, but my body just felt relaxed and like I finally allowed it to rest for the first time in 8 years.

I tried reproducing that sleeping positions in the following days but I haven't been able. Last night was just as horrible as the night before. I swapped between the couch and the bed, and didn't get more than 3x1 hour of sleep all night. Woke up with the usual fog.

Question: is that effect that I felt from finding the comfortable sleeping position the kind of effect I'll feel after my first night with CPAP or could that perhaps more be related to my sleeping position?

I am the most comfortable sleeping on my back, but I just can't do it anymore, and when I sleep on my sides, I need to have my arms under the pillow and find the perfect balance for my head to rest on it, and it's impossible.