Questions & Answers about Siento la necesidad de descansar más.
Spanish has two related verbs:
sentir (non‑reflexive): to feel something
sentirse (reflexive): to feel (a certain way), usually followed by an adjective or adverb
- Me siento cansado. = I feel tired.
- Me siento bien. = I feel good.
In Siento la necesidad de descansar más, you’re feeling a thing (the need), so Spanish uses sentir, not sentirse.
Me siento la necesidad… would be incorrect.