I have a lot of active interviews at once. Should I start all of them at the same time?

No — sequence and prioritize. Focus your energy on the opportunities furthest along in the process. Push earlier-stage conversations out by a week or two so you can give each one the preparation it deserves. Hiring timelines are usually more flexible than they seem — companies rarely fill roles urgently, and most will accommodate your scheduling request unless candidates are at a final stage.