If he calls you frequently - his desire for sex is not satisfied
With the development of modern communication equipment, the telephone has become an important tool for lovers to express their feelings. Because it gives both sides of the communication a great deal of freedom - for example, they can't see each other's awkward expressions, and girls can't see their boyfriends shaking their legs, sweating and smoking nervously - so for introverted men, the telephone is simply the savior.
However, there is another situation. If a man who rarely talked on the phone in the past suddenly becomes diligent and keeps calling you, he must have the "urgent need" in psychology. In sexual relations, the "urgent needs" that happen to men mostly refer to sexual desire. In other words, his desire for your sex is obviously rising rapidly.
Most men will avoid showing strong desire. They absolutely do not want the relationship between men and women that they have tried to establish to be destroyed overnight. Especially the introverted men are more cautious.
If your man is also in a high level of sexual desire and discontent, he dare not say "I want to talk with you" even on the phone, but can't find a euphemistic expression, so he will have to taste the pain of anxiety and desire alone. He subconsciously wants to talk with you and satisfy his desire, but he can't say why after calling you, leaving behind the fact that he often calls, which makes you puzzled.