In my sleeping bag, in a tent, with two other buddies sleeping next to me. This was durning a 2 week trek in the wilderness. I hadn't blow a load in 5 days, and I needed to get a good night sleep. I pulled off my boxers, and slowly stroked the head of my cock till I nutted a strong load into the boxers I was now holding. (I was in my early 20s at the time, so every load was a strong load). I put my t-shirt I was using as a pillow in my mouth so I wouldn't make a noise when I came. Woke up in the morning, my boxers were now rigid with dried cum and basically useless. So I got up naked and found a new set of boxers in my frame pack. By this point in the trip nudity wasn't a big deal.
The next night after we had all gone to bed, I definitely head one of the other guys rustling in his sleeping bag for like 10 minutes after lights out. I think maybe he got the idea from me.
Hot story!