Your cortisol may be high at the wrong time of the day. Its a stress hormone. I had Insomnia for a long time and found a book from the sleep specialist that helped.
https://www.drorma.com/
Suggest working on wake up time to fix this. If you set and keep it very consistent every day without sleeping in or napping later, you can expect to get drowsy roughly 16 hours later. Consistency over time is key.