You might have sleep apnoea. If you also happen to not really feel rested in the morning. I know people that haven't had it diagnosed for decades and it turned their life around and they also finally dreamed again. As a "byproduct" of not bearly dying every night but resting.

IF there is a pathological reason. Can also just be you don't stand up shortly after your last REM-sleep and go into deep or light again. Might wanna just check with some smartwatch or just an alarm mid-sleep to check if you then remember stuff.