I'm a 30M and this has been happening occasionally for years. It only lasts for about an hour and happens a few times a year, but it feels strange.
The feeling is a pain running from my belly button to my penis. It feels like there's a cord that's tight. It usually happens after I've been hunched over and then quickly straighten my back. To reduce the pain I can curl up.
I've searched for this online before and have seen it mentioned in forums but I haven't found an answer. I keep meaning to ask my doctor when I see him but keep forgetting.