[KitsuneFr]

Yes, I know that. When first time I went to a true japanese restaurant I felt the same... Nervous, thinking "if my pronounciation won't be good, possibly lack of vocabulary, etc..."
But after an Asahi and a Ki-rin, I felt a bit quieter, and at the end of the meal, just before leaving, I made a good thanking so even the kitchen's guys went out to wish a nice evening.

But each time at beginning in a new restaurant the nervosity is coming first.

I believe it is normal. My english level is far from perfect, but I know I don't have to translate in my mind, all that I can write or say in english is coming directly by thinking in english.

In japanese I have a 500 words vocabulary and the basic grammary and conjuguation. So sometimes I arrive to think in japanese, but it is hard and it is simple short sentences.

So it is normal to doubt and being nervous, but we shouldn't give up anyway, if we want to learn and speak - がんばれ!