I can fall asleep almost anywhere. I routinely fall asleep in the break room at work. Once, I was helping a friend fix his car, and I fell asleep on his garage floor when he went inside to get water.
But in a hot metal tube tearing through the sky, with my neck all kinked? Get out of here, man.
I usually have trouble falling asleep and can’t just take a nap in the afternoon - never could.
But on a plane I’ll be asleep minutes after the engines started and I’ll happily sleep for hours through an entire flight. Something about the engine noise and movement of the cabin is very soothing to me. Same for trains, busses, cars.
And yet I’ll regularly lie in my bed awake desperately trying to fall asleep…
Sounds like you might benefit from some white noise sleeping at home. Can play it through your phone or even an old radio set to some quiet static.