Same here.
Elias hides most of the time (he's not 4 months yet)
I just leave him and whenever I can, I hold him in my arms, stroke him and speak in a calm voice.
I had an anti-stress collar for him, but he had an accident with that and my husband had to cut it away.
The first days we never saw him drink, just as well we were feeding wet food.
Succes!