Post-Summer Workout

From last fall through this past summer I work out. Usually start off slow, graduate up to heavy and cut by June. I’m tired by then, joints ache and all (I’m 42) and I take a couple months to sleep in, relax, at most go hike or walk. I purchased “Best workout plan for natural lifters 1” and my question is do I start with that this fall? I don’t want to necessarily jump into trying to do iso hold/ slow negative squats right out the gate and so forth. Recommendations? Thanks!