Some dogs don't have a natural "off switch" and will only lay down and relax when they're in their crate or passed out exhausted. It's important to teach our dogs how to lay down and relax, even if they aren't exhausted or it's time for bed.
This is part of my nighttime routine with Arya. Once she's had her dinner and plenty of play time. I'll send her to her cot and work on getting her to relax. I'm using low value treats (kibble) and rewarding subtle movements that tell me she's relaxing. This can include deep breaths, lowering her head, hip turning to the side, tail wag slowing down, slow eye blinks, etc.
By doing this every night, she'll start to lay down and relax on her own, without prompting from me. These exercises are great for teaching your dog to lay down and relax so you can sit down and relax!