DS is 4 and has been very happy going to nursery for the last 18 months. He's just suddenly started to sob and become clingy (he did this before when he was terribly unsettled at a previous nursery when he was about approx 18 months old). He is also very clingy to me again. I can work out what is going on. Is this normal? Should I speak to the staff to find out if something has happened to unsettle him?