Is there an adjustment period moving from a beta blocker (felt fatigue, etc.) to an ace inhibitor of equivalent strength?

Maybe: If you have been on the beata blocker for a long period of time or have been on a high dose you may go through a short period of withdrawal where your body is learning to function without the medicaiton. A common compalint is fatigue which should improve over time. That said, you should contact your md & tell them what you are experiencing & let them decide how to proceed.