I was intrigued by your request. here is my experience.
When I read your story of what you would like to read, I thought maybe me. Yea, yea, I know, the male ego, but who knows, maybe my technique, method is something you would be interested in reading about.
What triggers these episodes I couldn't tell you, but when the desire for self pleasure arises, it is very intense. All of my senses are concentrated on sex, and once this begins to happen, I do more and more to intensify the feelings. In the morning I shower and shave very carefully so that my balls and cock are very smooth. If I am especialy turned on I even shave my legs. This seems to make my whole body aware of any movement across my skin. I then slip into a pair of my favorite panties. My favorite type are a sheer string thong, this way I can feel fabric across my bare ass as well as across my sensitive cock. Just putting on the panties causes a hugh erection. of course I apply lube and stroke myself, running my hand from my smooth balls and up my swollen shaft to the now reddish tip.
Once the first clear drops of pre-cum begin I reluctantly stop and slip eveything back into my very smooth panties. Of course, due to the excited state, not all of my cock fits inside, and the engorged head is left peeking out. I can't help but admire my nice package.