While this may be a problem with individuals; You're not feeling comfortable enough with the girl as individual in order for touching her to feel smooth and "normal," this usually a general problem. And by that i mean, instead of not being comfortable enough with the individual girls you are not comfortabletouching intimately at all... with almost anyone. Even family.
Kissing on the cheek, extended hugs, or hand shakes. They intimidate you, maybe. The prospect of sitting with your arm around a girl is a romantic image but to actually image it physically quivers you.
I used to be like this, no joke, no fake sympathy.
The only REAL way to combat this that I know of is to simply start touching. I'm still not cool with random
kino on random people, but I am much more comfortable with intimate touch. I would no longer have trouble having sex in public. In fact... I have. In the back of a van.
The only way to get better at painting is by: painting.
Hope I helped.