Kibitzer: someone who offers unwanted advice; someone who offers unsolicited opinions
Kibitzer is a Yiddish word. Originally, a kibitzer described someone looking over your shoulder during a card game, offering unwelcome advice. These days, a kibitzer is an outsider offering unwanted advice.
Ultimately, kibitzer likely comes from the German name Kiebitz. The Kiebitz is a bird with a reputation for being annoying.
When it comes to using this word, I’d give you some advice. But, you didn’t ask.