I've had a couple of Vivaro's like this. It is a known problem, first step is to check & update ECU software. Did this on 3 iv'e done but made no difference. Also meant to make sure there is no extra load on startup.
If fault is still there, according to bulletin its an injector. So check leak off.. Again have not isolated a single injector as the leak off test has been ok.
So we replaced all 4 injectors, no.1 was siezed, removed head - they couldnt even drill out so new head! (Luckily it was a warranty job!)
Set of new injectors and vehicle fixed.

So my question is.. What is it with the injectors that causes this fault??