Rereading your OP, I guess my post wasn't really helpful. Duh.
Not sure what's available to you, but if I get sleepy early, I take a shower. - even a wash up,,or washing my hair helps. A cup of coffee. Go for a walk. These help me stay awake (used to go to bed early and up at 4:30 am for w*&k). Took awhile to change my sleep habits.
Not a movie fan anymore - stories all seem the same. I read a lot of free ebooks. Check iout the news of the day. Social media time. Solitaire, if nothing else. Ever try writing something? A good time to blog or journal. Take up poetry lol. Star gazing was mentioned. Crossword puzzles. Ever try drawing? A lot of inexpensive hobbies one can do inside a vehicle at night.
If you can't sleep in the morning, especially in cold, can you get dressed warmly and walk? Get warm via the exercise and, and maybe get back to sleep in an hour or so. Depends on where you're parked, I suppose. Sometimes my joints get achy and moving around, or even just up and stretching, helps out.
Tai chi outside the vehicle? Doesn't take much room and is good for you.