Bruh 
That’s because “nice” is literally the bare minimum that qualifies someone as a human being worthy of interacting with.
Do women like shy guys? Yeah, plenty. As an extreme extrovert, I prefer introverts.
Being a self-appointed “nice guy” usually means that person is not nice at all. Someone who hangs around women and puts on a show of showering them with praise and hanging off them for attention, all while silently seething that their “niceness” is not being rewarded.
I see people fall into the trap of considering themself “nice guys”, by which they mean they will literally break their own spine bending over backwards in an attempt to appeal to women, any woman, please, god, just let women pay attention to me, I have a girlfriend-shaped hole in my life and any woman will do 
Emotionally healthy women are generally disgusted by servility and neediness, which is anecdotally exactly what the self-proclaimed title of “nice guy” seems to mean nowadays. If you are genuinely kind, respectful, pleasant to speak with, have good manners and hygiene, and actually understand that humans are individuals, I would consider that meeting the definition of “nice” as a bare minimum personality characteristic.
Wanna understand and improve? Maybe time for some shadow work and introspection to figure out what makes you “nice”.
Maybe because you are staring at them and it makes them uncomfortable.
Actual nice guys don’t think of women as objects to be bought, sold, traded, or haggled over in a marketplace 
hope that helps
Shadow work can help with this. May I suggest Belial or Leviathan?
Nice guys don’t send weird creepy messages. If you are familiar with reddit, may I suggest the /r/niceguys subreddit for some great examples of what NOT to do?
Definitely sounds like you need some shadow work.
Also, this:
Best of luck buddy