Probably in my late teens. My parents were pretty dull meat and potatoes type. My dad never spoke about politics and my mum was fervently anti communist (and to this day refuses to believe communism can ever work, just look at the Soviet union and china! Oh china is only beating us now because they're becoming more capitalist!) so I was pretty conservative or libertarian. Because you know no world experience. I distinctly remember super hating green arrow in the justice League unlimited cartoon when I was like 18. Oh a big leftie who wants government to help people? What a joke of a hero!
Thankfully working and participating in a union, getting a degree in history from professors that seemed fairly liberal but not really in favour of capitalism or communism. Also my major concentration in history was military history (such a cliche I know sorry) but specifically ended up with lots of classes on the Soviet Union. Which made me more amenable to seeing other sides of coin. Learning that much of the popular western tropes about Soviet participation in the war were utter fabrications really helped introduce me to the concept that the west was desperately trying to reframe history around how the Soviets were incompetent and only won because the west was so awesome.
Disillusionment with Obama becoming a complete joke of a president, not accomplishing much of anything and the discovery pseudo left gaming spaces online helped guide me further towards things while I also fell into the Chapo subreddit and was introduced to how leftists are always right and we need to become communists or else everything is fucked. I think the west wing thing podcast helped alot as well.