My 10 Altima 2.5SL (only 47k miles) has developed an intermittent soft metallic rattle. I hear it most often on accelerating. Car runs fine otherwise. I understand CVT's & engines can make noises as they are going bad, but somehow this noise sounds 'superficial' rather than something from deep inside the drivetrain. I'm wondering if my noise could be something like a heat shield or maybe an exhaust hanger/etc. I don't have a lift to check stuff easily. Any suggestions about where to look before I get under the car on a 'blind' search?
Any educated guesses???

Sorry, we must have missed this post. Yeah, a heat shield is the best educated guess. But it's been a few days. Have you managed to do any under the car listening already? I'd have a friend hit the throttle a bit (in park with e-brake on of course) while you listen. Also, try and see if it does the noise when you coast, in park, in drive, while idling, while revving, etc.

Late reply, but swamped with life lately
Altima seems to run OK, and no noticeable drop in mpg's (I've always kept mileage & fuel logs for my cars).
If I put the car in drive and gently rev the engine I can reproduce the noise. I have not recruited another diver (that I trust!) to repeat this maneuver while I listen underneath the car. I'm in the Midwest & FWIW the car still has its original exhaust system. I've had exhaust rattles in other cars but this seems like a softer noise. And only intermittent during normal driving.
I'm due for an oil change soon. When I take it in I may ask the dealer for their 'diagnostic fee'.

Could be an exhaust leak paired with a heat shield rattle. Those show their face more when you're on the throttle and the pressure builds up a bit more inside the exhaust piping. Up on a rack would help locating the sound for sure, but still requires someone to sit in the seat and hit the gas. Good luck with this and all other aspects of life.

Thanks!
Will post again when I find out more.

It could be the maniful/catalytic converter heat shield , my car have that part loose because the screws are corroded and they are thin now, so I don't want to try to unscrew and broke them

My car is an Altima coupe 2.5 2008

Don't overlook the belt run, a slight acceleration can make noise there too if say a bad tensioner coming up.

As well, not sure of the exact mount placement there but whatever that passes for the trans lower rear mount can do the same as well when the chassis loads up from engine twisting on the mount. Sometimes depending on how designed even gravel off street can get up in there to do a wonky noise like that.

If heatshield you can sometimes even hand bend the most likely place to vibrate to stop it. Just bend it a bit different to change the resonant frequency there. I did it on Focus cars all the time, they left a big piece pretty unsupported that tended to do it.

Dealer finds no fault codes with the CVT- and fluid has "plenty of life left". So looks like I'm left tracking down heat shield &/or exhaust noise as most likely culprit. Weird thing is- no noise driving to or from the dealership. Can cars act like little kids who stop complaining 'cause they don't want a shot when they go to the doctor's office

Yes, cars can sense when they're going to a dealership. They either stop squeaking, squealing, chattering and sputtering if going in for diagnoses, or they start all the above if going in as a trade in for a new car! If it makes you feel better, mines developed a nasty rattle to, and it's a new exhaust! I haven't spent the time underneath to find the source yet, so I can relate to yours taking a while to get at.

I bet it's the F'ing exhaust manifold shield. There's a service bulletin about it too!

https://www.carmd.com/Tsb/Download/95615/1tw27

Take out the black plastic intake piece above the radiator so you can access the exhaust manifold, just two bolts facing upwards. Then look and touch and move the manifold shields see what you find. Try to twist those bolts, maybe they're loose.