Dear mothers, one more question. Son is 3.5 months old. He's putting h…

Dear mothers, one more question. Son is 3.5 months old. He's putting his whole fist in his mouth. And lately he's become too restless, constantly crying. Teething hasn't started yet, I massage his gums with a special rubber brush. There's a lot of saliva now. Is this a sign of teething? (I attached a photo, it looks like he's sucking all his fingers)