Intermittent chattering/rattling noise at about 25 or 30 mph.
Sounds kinda like a card in bike spokes but at a slightly lower pitch.
It may occur at higher speeds but the engine may be drowning out the sound.
It comes and goes while coasting or accelerating seemingly independent of the gas or brake. It lasts for about 6 seconds then stops.
I notice it mostly when I pull into my subdivision at low speeds.
Any ideas? Thanks in advance.

 

Exhaust rattle, worn wheel bearing, random natural disasters waiting to happen.

Maybe someone tucked a playing card into your brake caliper?

Seriously though, go to a local lube shop and tip them to use the pit for a few minutes so you can get under it while the engine is running, have their tech rev the engine a little bit while you listen for where the sound is coming from. While under there look for debris like tumbleweeds stuck in the under part of the chassis, a few months ago I had this insane rattling sound from under my vehicle it sounded EXACTLY like there was a plastic bag under it fluttering around and it turned out to be this little TWIG stuck in my chassis that was barely touching the asphalt, I even saw it multiple times when looking under my vehicle but thought there was absolutely no way in hell that sound was coming from it.

It was...

 

Yes on the exhaust,,, maybe heat shield, or shields....

 

Thanks for the feedback.
Card in spokes is actually a bad description.
Its more like a cat loudly purring.
It starts and gets louder near the end, then abruptly stops after about 5 or 6 seconds.
Almost like a valve is sticking and then releases.
Its driving me crazy.