Hiden public in apartment building
 

When I was living on the second floor of an apartment building, I sometimes let randomly (using a die, a coin or cards) decide whether I had to fetch the newspaper from the mailbox naked. I only switched on the staircase light the first time. But I regretted that immediately, because I could be seen from the parking lot. And I couldn't even look outside because everything was reflected in the windows.
Luckily, I never got caught. The newspaper was always delivered very early. Probably all the neighbors were still asleep.

In the attic we had a large common room on each side of the staircase. On the left was the drying room for laundry. On the right side, storage rooms were separated for each tenant with wire mesh.
Every now and then I just went upstairs and undressed naked. Most of the time I quickly masturbated and then put my clothes back on. Sometimes I also tried to delay the orgasm as long as possible.
Usually I only wore T-shirt and sweatpants for this purpose, because you could quickly put them back on when someone came up. If I wanted to raise the difficulty level, I wore shirt and jeans instead. The highest increase of risk had been to put the clothes in my storage area and then walk naked into the drying room on the other side.
I was rarely interrupted. And with one exception, I always managed to get dressed in time. Only once I hadn't heard a neighbor in time and had no time to get dressed. Luckily, someone had previously hung up some bed linen and I was able to hide behind it.