Curious about how others handle fatigue

I'm 53 years old and I have shifted my workout from doing specific body parts on certain days, to doing a full body workout on Monday, doing cardio on Tuesday and resting on Wednesday. Repeating with Thursday and Friday and resting on Sat. and Sun.

In spite of all this, I still have fatigue after working out for about 3 straight weeks. At that point, I basically skip a routine (not a full week), which would give me like 5 days of rest. After that, I seem to be rejuvenated and go another 3 weeks or so.

My question is, does anyone else have this fatigue problem and do you work through it or do you rest when you feel it?

fatigue comes into play with other factors such as diet, sleep, and what you do during the day.