Giggling is one of my vocal stims and I sometimes do it when I get a funny thought in my head, or when I have a lot of energy to burn off. But I do control this when I am in public.
When I'm with other people, I don't really laugh at anything. I tend to laugh more at hearing other people laughing, rather than at what exactly has been said or done to cause it.
_________________
I'm sailing across Spectrum Sea, in my little boat.
The waters of the port were choppy. After I set off, there was a long, massive storm.
Years later, however, the sea calmed. I'm still on tranquil sea, but I'll never reach the Neurotypical Beach.