Odd question I know!
We've been to a couple of different vets and they can't find anything knowingly wrong with our cat. She goes through phases of randomly mewling, it seems to distress her a bit and used to be accompanied with noxious farts.
We swapped her diet out for something more natural that she also likes and that seemed to deal with it, but our vet then said a few months ago she was getting tartar and recommended we put her on dental biscuits only. This has been largely ok until the last couple of days when the mewling, though thankfully not the smell, has returned.
She's an outdoor cat, so we assume she's decided on having some food at someone else's house.
Has anyone else's cat gone through similar? If so, has anything helped. We'd prefer not to have to lock her in of course 
TIA