For me it’s probably if i see my partner being flirty with others or others being flirty with him.
It doesnt happen often these days, much more when we were younger lol.
He doesn’t do it on purpose, to make me jealous or anything though.
He just likes to joke and act silly to impress people but when he does it in front of girls then i get a bit jealous.
I always think a bit of jealousy in a relationship is healthy.
It shows you care about each other, and i know he is the same with me.