E36 325TDS wobble at idle

I own a 1994 325TDS Auto with 88k miles on it. It has been running well but recently it's developed a natsy wobble from the engine at idle. There's no sign of a problem once moving, performance is fine. The air
filter and fuel filter have recently been replaced, I've run injector cleaner through it, a local non-specialist mechanic has looked at it all to no avail. This has come on gradually, a while ago it gave an occasional wobble, now it's continuous. It's not running irregularly it's just got a rythmic wobble--a bit like a petrol engine that's running too rich, only worse.
Can anyone suggest the most likely cause or suggest what I should investigate and how?
I'd be grateful for any assistance anyone can give.
Howard Taylor
(Chandler's Ford, UK)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.