Waiting mode is a term many people with ADHD use for a familiar experience: with an appointment or call later in the day, they cannot settle into anything beforehand. The upcoming event takes over, and the hours before it slip away in half-starts and clock-checking. It is not an official diagnostic term, but it is widely described.
Planning around it usually works better than fighting it: put appointments at the start or end of the day where you can, fill the waiting time with low-stakes tasks that are fine to drop, and set an alarm for when to leave so you can stop watching the clock.