When I drive at times, especially uphill I get a low frequency shaking and hum from under the hood. If I take my foot off the accelerator and then put it back on again the noise goes away. Performance of the car seems otherwise ok.
Turn the engine on, open the hood, stick your head under, and manually activate the accelerator linkage. I’ll bet you’ll find the source of the resonance.
If it seems to be coming from under the car, put the car securely on ramps, slide under, and start shaking things. Start with the heat shield on the cat converter. They often come loose and rattle. If it is that, you can repair it by securing it with a large worm-type nose clamp from the hardware store.