hi it can be due yo teething and at this age baby start exploring everything and they do it by putting it in mouth, also its way of learning for them as they will be using hands for eating :) you should keep clean toys near him and keep n eye he doesn't do it all time to avoid choking n unhygienic things going inside mouth

babies start teething as early as 4 months

babies explore their surrounding by putting things in their mouth. it could be just that...

Every baby of his age put things and toys in their mouth, it's the way they explore things around them. and as you mentioned teething also can occur at early stage

yes some babies start early.. teething could be the reason.