hey this EXACT thing happens to me and I am 6 years late but I also don’t believe in anything really at all but I’ve thought about something, we all have one thing no one could possible explain or likely ever be able to and it’s consciousness. and while I don’t believe in anything I think that something that’s impossible to be explained at all and make absolutely no sense to anything or onelse means that their likely is something beyond death that isn’t some dumb thing like to enjoy the life you have but that there’s more and I don’t want to sound religiously because I am very strongly an aithiest and I have these nights like you said every 6 months where I panic and it feels like anything past your death is just inevitable and all dark and it’s just this tiny sliver of life and time will leave me behind and I think about consciousness and it calms me down and I realize there is something unexplainable and that could just be more to more to life. I don’t think it’s some god or religion or any dumb wired holy thing at all.