I need advice

My 3.5 year old son has recently started, what his teacher calls, “self harm” when he is having a meltdown. He screams and cries, getting all red in the face. But the concerning part is that he grabs at his body and yanks on it. His teacher said he was grabbing at his throat and his chest. Like grabbing and pinching. I don’t understand where he could be getting it from and it just recently started. Is this something all kids do? What should I do about it? Because I’m worried people will start to think that I hurt him and he’s my baby. I’d never lay a finger on him. I just don’t know if I’m doing something wrong or what is going on here. Dad isn’t around. It’s just me, my mom, and the daycare.