Hi, new here so I hope I'm doing this right...

I was in the pub last night and a guy started singing this song, I never got the chance to ask him the name and my memory of the lyrics is somewhat patchy...was wondering if anyone could help?

Basically, it started with something like "I didn't want to sing tonight" and the chorus was along the lines of "It's a lovely song, but I'll get it wrong, 'cause I'm shaking at the knee". There was something about having never used a mic before, and something about it having gone alright at home. That's about all I can remember I'm afraid, but if anyone knows the song and could post the rest of the words that would be very greatly appreciated!

Thanks