I’m always very wary of people who feel the need to declare their positive personality traits, particularly in a dating scenario. A guy who proclaims to be a gentleman, or a nice guy, or a hopeless romantic, in my experience, very rarely is.
The truth is, people who are genuinely decent and kind-hearted don’t have to put on a show to exhibit their awesomeness, we know them to be so from their behaviour.
And someone who only exhibits “nice guy tendencies” as a way of impressing women, is far from genuine. Real kindness isn’t something that you switch on/off depending on whose company you’re in.
Proclaiming it doesn’t prove it. If I’m hearing about your supposed niceness more than I’m actually seeing it, then you get an A for charisma but an F for effort, because your words aren’t translating into anything meaningful.
Basically, if he calls himself a “nice guy” but always finds a way to turn everything you say back into a conversation about himself, or if he’s forever caught up in whatever is going on in his own life to ask about your day, or if he makes douche-bag comments followed by “I’m only joking!”, or if he claims to have strong feelings for you but is never there when you actually need him, then it’s highly likely that all of his “niceness” is a disguise for a deeply self-absorbed nature.
My advice: RUN!