I've rested a while since completing my most recent manuscript. I immediately sent out several queries, but that was a mistake.

Why? Because the query is a constantly evolving tool. Each time you get a rejection, you look at the query and think - why in the world did I sent that? That's awful!

So eventually it's modified sufficiently and is catchy and compelling and people start responding.

What's the point?  Try to save your best prospects for later when you begin querying.

My latest query is good and I got an immediate response asking for a full manuscript. No guarantee that the agent will be interested, but at least my foot is in a door.