i think this is manifested in different ways for men, different, but very particular and consistent ways.
op let me tell you a couple of stories about my experiences with this.
just for context, i am usually very good and comfortable with intimacy. i was always comfortable with sexual intimacy and through the process of a couple of worthwhile long term relationships i became comfortable with relationship intimacy. (vulnerability was one of those things i had to grow on.) so i have a lot of experience with the sexual connection; the way you are open and connecting with your partner during sex.
i had a bf who the first time we slept together it was obvious to me he was blocking the connection. the entire relationship we struggled to connect with each other during sex because he was guarded and had walls up. we had a few blissful times together in the honeymoon period, which tricked me into thinking i just had to get past his barriers. but after awhile, he would close right back off again. there was only a sweet spot of window of him being willing to connect with me, and that wasn't who he was - the guarded closed off afraid to connect person was who he was.
so, ok, i learned from that. second example: i had a friend with benefits. now for me, if i have a "FWB" there actually is a friend component to the relationship; not just the FB thing. so we were cool enough for him to tell me, during one bout of our off and on FWB relationship (depending on what we had going on with real life dating, it wasn't consistent) that he had developed impotence from masturbating too much. apparently there's a new thing called Porn Induced Erectile Dysfunction. what this meant for him was that he would masturbate out of boredom and not even being aroused and eventually, since he had trained himself to complete masturbation with a penis that wasn't even fully erect, normal arousal and normal sexual functioning just stopped.
you know what i else though? i went right on and connected this to his discomfort with intimacy. we were hooking up (due to his little problem
the sexual relationship was different, but still prsent) and we were literally talking and in contact all day every day and yet... when we were together, even though we'd have a great time, i felt uncomfortable being able to be affectionate with him. he was the kind of guy who would take it the wrong way and to mean a whole different coloring book of nonsense if i randomly wanted to hug up on him or kiss him. and if i had to have some stupid conversation and reassuring him that i wasnt catching "feelings" for him every time i wanted to touch him, like, that's just stupid and too much work for me. i have had no strings attached relationships with the full blast of physical affection that stayed no strings the whole time. so his weird reaction to physical affection being to the point where i felt like i couldn't even be
nice to him, like, there's too much going on for me and i don't have time to be banging someone who freaks out if i want to hold his hand.
now... im not saying these things are ALWAYS related and connected. BUUUUUT, if you do notice any funny business with masturbation or inability to function properly during sex... keep the antennae up.