After how many dates, do you start worrying about a lack of physical intimacy?

We are both in our early 30's. We have been on about 12 dates over the past 3 months. I usually initiate the dates but she always says yes. She responds to my texts quickly. However, she is a bit reluctant to be physical. The most we have done is kiss for a couple of seconds. I'm not sure if she just likes to go slow or is just not attracted to me. I plan on talking to her about it but wanted to see if any other men have been in a similar situation.