If a guy all of sudden gets nervous?

around me but normally is not, he is very confident and I have a feeling he is into me. He is very confident around me giving eye contact but one time he became nervous around me, while saying hi and how are you. I felt so bad for him, I wanted to say something to him but I couldn't. Does that nervousness that one time validate it more that he would be into me even though it only happened once?
If a guy all of sudden gets nervous?
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