sink backing up again, what gives?

Okay, so this is like the third time in two months my kitchen sink has decided to rebel against me. It starts with a slow drain, then suddenly it's like a mini swamp in there. Gross, I know. I've tried the usual stuff - plunger, drain cleaner, even that baking soda and vinegar trick my mom swears by (spoiler alert: didn't work).

I'm starting to wonder if there's something bigger going on here. Maybe something deeper down the pipes or outside the house? I live in an older place, built in the late 70s, so I'm guessing the plumbing isn't exactly state-of-the-art. But still, three times in two months seems excessive.

My neighbor mentioned something about tree roots causing issues with his pipes last year. Could that be a thing? I mean, we do have some pretty big trees around here. Or maybe it's grease buildup or something else entirely? Honestly, plumbing is not my strong suit - I'm more of a "call someone and hope for the best" kinda person.

Has anyone else dealt with something similar? I'm kinda hoping it's not gonna be a huge expensive fix, but at this point I'm just tired of dealing with it. Any ideas what might be causing this mess?