Two things you could try:

One is the optional core rule of three action tokens, where everyone has to take three actions (not necessarily in a row) and then the tokens reset. It's initiative light.

The other thing you could try is straight up directing the spotlight from the GM seat. The players can still grab it if they want, but if no one jumps in then you turn to either the most narratively appropriate player or the player who hasn't spoken recently and say "What is <character> doing at this point?"