Help! Annoying rattle sound from Exhaust
 

Hopefully someone out there has experienced this noise as I've heard them from a few different caddys. When I either turn the ignition on and wait a few seconds, or fully start the motor, there will be this annoying rattle sound emanating from what seems to be the exhaust or somewhere towards the back of the car. It comes and goes especially when driving. I'll try and post a video but essentially it sounds like some little pump has turned on and it's quite loud and when I drive around with the windows down it's completely embarassing and annoying. Has anyone experienced this?? Thank you for all input.
By the way, its a 98 eldorado

It's the Electric Level Ride pump for rear shocks.

You know that was initally my first thought since the car rides a little low in the rear. It goes on and off though and never stops, does this mean that one of the shocks is leaking? I hope not sounds expensive. Thanks for the reply

Check air lines to shocks for breaks or being disconnected. Also check condition of air boots or bladders on shocks for cracks or deterioration. If everything looks good you likely need pump which is somewhat expensive.

I have had this problem and found the air line touched the exhaust and melted the line I spliced in a new piece of line with compression fittings and thought that would fix it but them air lines are so tiny any debris can clog them its best to pull off the lines and see if air can be blown through if not they need to be replaced. Not sure how much the dealer price is for the line but I bought a air line kit from Napa auto parts for 18 dollars the only part you need to keep is the duel end that plugs into the compressor