Good point. The main reason I was alarmed is because it's so uncharacteristic of him. I checked on him this morning and I can touch him without him thrashing but he goes into strike position.
He's been aggressive once before when he had a slight burn on his head years ago (newbie keeper error), which makes me think that maybe something hurts or he's not feeling well.
I'll keep an eye on him, thanks all for the ideas and advice.