drhtati

1. to tremble; to shiver
   Dete je drhtalo od hladnoće na stanici. — The child was shivering with cold at the stop.
   Ruke su mi drhtale pred ispit. — My hands were shaking before the exam.
2. (+ nad someone) to fuss anxiously over; to be overprotective of
   Baka drhti nad svakim unukom. — Grandma fusses anxiously over each grandchild.
3. (+ za someone, something) to fear for; to worry about
   Cele noći smo drhtali za njegov život. — All night we feared for his life.

The cause is expressed with «od» + genitive: drhtati od straha.