It is not unusual to have some problems with initial affection when meeting someone, even someone you know and love very much. It actually has a name. It is called proxemic shyness. Why does it happen?
Our personalities, our own unique development, and even our past family histories all play into how we make that connection. For some, that connection is easy; for some others, like yourself, that connection may involve feelings of insecurity, self doubt, shyness, even fear.
Most often this is totally harmless, and as long as you communicate with your partner that you want to connect but sometimes feel too shy to do so things often are fine. Most people are flattered that you would trust them with this level of openness and will respond with care and concern and understanding.
However, if you feel that this issue is not something that you are comfortable with, even though it is very common, you can deal with this through seeing a counselor who can help you explore your shyness and hesitation and to resolve it. Usually this is very simple and quick, as most issues like this are caused by family development and fears related to rejection. A therapist who practiced a technique called cognitive behavioral therapy can help get past this issue. CBT as it is called is well respected and researched and is a commonly practiced form of therapy. You family doctor should have several resources to CBT counselors in your area.
Please know this is common, is not unusual and can, if it bothers you, usually be resolved easily through a short number of sessions with a behaviorally oriented therapist. Steven