Sounds like the moose (V6 only problem) to me, except it usually gets people when the weather turns cold. Even so, it could likely be a bad IAC. Would explain the resonance and the rough idle (IAC can't control the air going into the engine properly).
You can:
1) clean/replace the IAC
2) do the TH fix
Probably #1 if the IAC is shot would be the only way to go.
