Are we talking Inclined Bed Therapy here or something altogether different?
Anyway if it's IBT - I also have sleep Apnea and sleep with a CPAP machine every night. Mrs M has MS and has had CCSVI treatement.
Our first few nights were odd, I'd find myself sliding down the bed and it felt altogether strange, however after a few nights it felt normal and now when we go away on holiday now a flat bed feels odd.
Experiment with pillows, it could be as simple as that.
We lifted the head end of the bed 100mm (4"). Any more than that doesn't work for us.
We're not all the same - try different lifts, but give each one a week at least - going from level to inclined is always going to be odd to start with.