The inner CV is a tripoid spider that sits in a cup that clips into the transmission housing. They can wear out and grumble.. though 50k miles (I think I saw your mileage on another post) might be on the lower end of how long it can last. They grumble more when the suspension is compressed or extended (accelerating over a crest or hitting a dip on the motorway etc.)
If you get under the car, try to rotate the driveshaft by hand, and/or move it in and out. There should be zero or practically zero play in it.
If you're feeling adventurous, you can pull out the driveshaft (you'll need to remove the hub nut and unbolt the damper and caliper from the hub assembly.. but it's not as bad as it sounds) and have a look at the spider.
The good news is that a grumbly spider can carry on for years.. I had one pack up on a road trip in France in 2017 - the needle bearings on one of the rings gradually fell out, but the rings mashed them to a pulp as it went, and it carried on fine, becoming more and more grumbly for another couple of years before I swapped it..
It's worth swapping them sooner rather than later though. You ought to be able to find new tripoids separately - they're only held on with a circlip but could be seized on/tricky to remove (although bashing them with a hammer usually works). New one similarly taps on.. but you need to be more careful, obviously.
Otherwise a new driveshaft is not much more expensive and you get new outer CV and boots etc. so it's probably just as cost-effective a fix.
Ralf S.