Ashwagandha (Withania somnifera) is an herbal adaptogen for the adrenal glands and stress related issues. Adaptogens are substances, often herbs, that affect an organ whether it is overactive or underactive. That is, adaptogens have the effects of both lowering an over functioning organ and raising an under functioning organ, whichever the organ needs. Since many organs including our anti-stress glands, the adrenals, overwork for a while, and then collapse, and then overwork again, adaptogen supplements like ashwagandha are useful to take in any circumstances.
So if you feel bursts of energy on some occasions and fatigue or exhaustion on other occasions, this might be a pattern where ashwagandha would be appropriate. You can try it for a month and see how you feel. If there is no effect noted after one month, ashwaganda is probably not the nutritional support you need. If however, you notice an improvement in energy and a balancing of the highs and lows of your energy, then ashwagandha would seem to be a valuable supplement, especially in times of increased stress.
Ashwaganda is in the nightshade family of foods, and anyone who is sensitive or allergic to these foods (potatoes, tomatoes, eggplant, all sorts of sweet and hot peppers, paprika, tobacco, and a few others) should avoid ashwaganda.