What is a nervous laugh, how can people laugh if nothing funny happens?
It’s just an automatic response. Some people laugh when they get nervous, they can’t help it. When I was walking down the aisle at my wedding I had this irresistible urge to laugh and it took me all my time to control it. Some people laugh at funerals for the same reason. The impulse gets less and less as you get older, so don’t despair!