I used to have sleep apnea before I lost the weight (125 lbs). My level of “desire” was pretty low. Another recent study shows that obese men with sleep apnea have lower levels of testosterone in their blood. The men in the study, on average, were exactly the same weight I was at my greatest (337lbs). The men in this study had severely decreased sexual quality of life; the bigger they were, the worse it was.
One symptom of sleep apnea is daytime sleepiness. This man (waiting in the train station) probably sleeps better sitting up during the day than laying down at night.
If you want your “stuff” to keep working, work out, lose weight, and reduce saturated fats in your diet. If your “stuff” is not cooperating, see your doctor to ask if you should be evaluated for high blood pressure, diabetes, heart disease.