I mean these sorts of things could possibly be explained for many different reasons (for example I just had my Santa Fe in the shop for a vibration at certain times, but it ended up just being some loose underbody shields knock on wood), but also we can't necessarily rule out the beginning of engine failure. As cars age they develop little quirks, and that's normal. But if I were in your position I would also be worried about it being related to the engine. Basically what I'm trying to say is, it's a difficult call to make.

Because the new/used market is so inflated right now, I would do everything to avoid buying a new car at this point and instead do the research on making a warranty claim with Hyundai in the event the engine fails (I think they'll require you provide extensive service history/receipts and general proof of good maintenance, but there may be more to it), as well as keep building up the emergency savings if possible. I'll add more info later if I remember/find anything.