Originally Posted by: navyguy778

Is this normal for an older beginner or am I doing something wrong?

Entirely normal IME.

Obviously going to be exacerbated if your muscles are A. not used to exercising your left (?) wrist with the vigour you now are fretting, and B. suffer from any of the myriad of degenerative age related conditions about your wrist, arthritis, previous fractures or injury just general muscle loss of strength.

If it's not hurting, then it doesn't sound like you suffer from arthritis. Fatigue is just like will occur in any part of the body being used again which has been neglected for an aeon, especially with the intensity fretting requires.