2005 Honda Accord Radiator Problem?

I'm currently in the process of trying to figure out why my car makes a vibrating noise (often during idling and sometimes while accelerating). The pedal also vibrates when you hear the noise. I have already changed the air filter and spark plugs (per 2 recommendations), but the problem persists. I notice that when I turn the air conditioner on, the noises/vibrations occur more frequently. Then, I noticed that every time the engine cycles on, these vibrations occur. My next guess is that there is a problem with the radiator or radiator fans, because it seems like they are either loose or working very hard (turning on frequently). However, I'm not a car expert, and so, I'm just not sure. Could it be the radiator or perhaps a thermostat that is causing the problem? Thank you.