What will automatically make you trust someone?

Their smiles, nods, good listening, and how much they agree with you.

Nothing makes me authomaticly trust someone / nothing authomaticly makes me ...

in such an absolute manner

Explanation:

Trusting someone / anyone to some extent is probably the healthiest (human) psychological characteristic because there is a natural balance between personal interest and general interest (under normal conditions of pressure and temperature). Yet, the more we learn, the more we tend to forget and the parameters of the fragile equilibrium tend to change