"Хотеть" is a verb directed at something.
"Хотеться" is a reflexive verb and it goes by itself or directed at self.
For example: "я хочу есть"/ "I DO want to eat", it's my active desire.
"Мне хочется есть" / "I have a strong desire to eat". So, it's not my active doing, it's just what I'm thinking about right now.