I'll be replacing my cold start injector sometime next week, my car has the same problem. Ill let you know my result

Head gasket
Where abouts is the cold start injector

On the end of the intake manifold to the right of the throttle body (with the banjo connector)
 

Lumix
My 97 NA use to do this. In my case I discovered it was the Caltex Vortex 98 fuel causing my cold start problems. So for an experiment, I filled up with BP Ultimate 98, no shuddering. The next tank I tried Shell V-power 98, no shuddering. I went back to Caltex Vortex 98 and the car shuddered on the first cold start every morning until the tank was empty. I could turn it off and restart the car with no problems on the second start. No idea why but using a different fuel has worked for me, possibly something you can try when you fill up next? 

Ha ha, that's interesting.
It so happens that I have just started using Caltex Vortex 98, (I had not used it previously) and now I think about it that coincides with this problem starting. I've also never had the problem before.
Next time I'll fill up with Shell or BP to see what happens.
 
When I find out, I'll post up the result.

I use caltex 98 all the time and lately I haven't had the problem at all. Seems to happen for a week or so then go away for a while.