Make both shapes separately
Start with the Em and Am diagrams and check the intended strings of each shape. Em can use all six strings; our Am shape leaves string 6 out. Find each chord independently and pick its strings one at a time. If the same note is unclear every time, that is a useful specific task to work on before adding a timed change. A teacher can help you identify a position issue or whether the instrument itself deserves a setup check.
Watch where the fingers are going
With the fingerings shown here, Em uses finger 2 on string 5 at fret 2 and finger 3 on string 4 at fret 2. Am uses finger 2 on string 4 at fret 2, finger 3 on string 3 at fret 2 and finger 1 on string 2 at fret 1. Notice that the pair shifts to adjacent strings and one finger is added. Observe the movement slowly rather than trying to land at full speed.
Leave the beat out at first
Form Em, release the shape and locate Am without a deadline. Pause, inspect and listen. Return the same way. You can practise part of the movement, such as locating the two adjacent second-fret notes, before combining all fingers. Keep movements manageable and take a break when needed. A count of hurried attempts is not necessarily a useful measure of how clearly the change is developing.
Use an intentional gap
Try a strum of Em, leave space for the move and strum Am when ready. If a regular count helps, give the change a planned gap instead of pretending it must happen instantly. For example, in a slow four-count, strum the current chord on beat 1 and use the remaining beats to prepare the next. This is an original practice pattern, not a transcription of a song. Begin without the metronome if its click adds unnecessary pressure.
Notice one improvement and repeat the useful version
Look for a more predictable movement, an intended string that rings more clearly or less need to inspect the whole hand. Keep one simple note for next time. If adding a pulse makes the shape unclear again, return to a slower or untimed version. Speed is one variable you can change later; a steady practice routine also depends on listening and keeping the target understandable.
Put one idea into practice
Find a chord shape · Make a session plan · Use a steady pulse