Startling behavior, what is this!?

Last night my male chin, Bentley, did something strange that I've never had him do before.

We discovered he loves organic rolled oats, it's like a drug to him. He goes bonkers when we give him some and will practically maul us for more.

He was out last night and I fed him a couple small pinches and decided that was enough. He decided he wanted more and grabbed the baggie that held the oats.

I took it away from him and said no. He grabbed my hand tight between his two front feet and also grabbed a bit of skin in a pinch. Then it seemed like he was humping my hand. Or jerking it around or something. He startled me and I got scared because I thought he would bit down harder on my skin though I barely felt his teeth and he didn't even leave a red mark.

I pushed him off my hand and told him, "No". He did it again and I kecked at him. And he let go and ran away. Afterwards he was his nice polite little self again.

Could someone please tell me what happened!? Was that a temper tantrum, an act of dominance? Once chins do that do they begin to bite more?

I have an irrational fear of being bitten. Does this mean he's crossed a boundary and will begin to bite?