This happened to me all the time, for decades. Nasal strips seem to be helping quite a bit. I say 'seem' only becasue I have experienced periods where sleep gets better (although never normal) only to relapse. I have bought many different kinds, looking for balance between cost and what works and the ones I link to are by far the best I have tried.
If there is a sleep study doc/program near you that might also help. Sometimes this problem requires a CPAPA machine. There are several areas in the respiratory area that can lead to sudden sleep interruption.
Good luck! There is not nearly enough enough attention being paid to the ultra serious and widespread problem of sleep deprivation.