estaban trepidando
-they/you were shaking
Imperfecto progresivo para el sujeto ellos/ellas/ustedes del verbo trepidar.

trepidar

Cuando la encontraron, después de muchos años, muchos en mi reino estaban trepidando.
You know when they found you after so many years there were many in my kingdom who were trepidatious.
Palabra del día
el muérdago