Why am I getting irritated so easily all of a sudden?

I have been a really laid back person my whole life. I am currently 29. About two months ago I started getting irritated really easily at stupid things, like someone drinking too loudly or if someone is telling a story and I feel they are taking too long to tell it. I start feeling angry like I want to yell at them, but I don't know why. I have learned to keep my mouth shut in these situations or I making a snappy comment, but it really hard to control my emotions all of a sudden. I quickly try to excuse myself so I can go vent to myself in private. Is there like a psychological issue that can cause this?

And before people say it, I know I am not pregnant and I haven't had any major life changes this year.