Almost all Flows are being queued

Almost all Flows are being queued

A few days ago I saw one of my Flows status was Queued. This was the first time this had ever happened.
Now, almost every Flow that triggers is Queued for at least a few minutes. If I re-trigger the Flow (which causes separate problems) they sometimes process immediately.  

These delays are obviously causing us some issues. My questions are:
  1. How can I resolve this?
  2. Is there a reason this suddenly started happening? 
Thank you for your help!