The same thing happens to me, but I can fight it. The problem is I put my kit in the wash and hop in the shower immediately after coming through the door. So I go from dirty and uncomfortable to clean and comfy rather quickly. I usually can't help but crawl into bed right after this process and the end result is that I can pass out pretty quickly. I usually only sleep for 10-15 minutes, just like you, before I snap out of it and go out for a nice dinner and beer.

I think that's just how it goes when you punish your body for 5 hours.