I have an 09 1.8tdci which has been well looked after..so last week I was driving at 60mph when the car made a engine judder,after 15 miles it do it again and came up on the display engine malfunction and went to limp mode..called green flag who said no fault codes will be found as no engine management light on..restarted no bother and no display of engine malfunction light..tested it anyways and no fault codes found..has been into a garage for diagnostic and again no fault codes found..so I’ve asked 3 garages what it could be with no luck, I’ve been out in it again this morning and within 3 miles did the judder again it’s very noticeable but it didn’t throw up any lights or breakdown..this car doesn’t have a dpf..it’s had a timing belt done last year also new glow plugs and fuel filter 8 months ago...I’m struggling to know if it the erg valve or injectors, how would I find this out?

It might be worth changing the fuel filter again just in case you've used some dodgy fuel in the last 8 months, cheapest thing to try first.  

EGR almost always causes fault codes so it's probably not that.  I'd suggest it's likely to be an injector fault, you won't really be able to test for that yourself though, needs a diagnostic live data test, or a leak off test done.

I'd say fuel filter too.
On the 1.8 engine there isn't any official change period quoted so it doesn't tend to be done during a service but I personally recommend every 12 months.
You must change the filter and seal at the same time.

Sent from my SM-G965F (S9+)