My Vieleds do it all the time.
They arent smart enough to move from the basking spot, so you need to change your bulb wattage.
Nobody asked you what your basking temps were.
Do you have a lazer temp gauge?
These are great for reading body/basking temps.
My female usually only does it when she is done eatting.
She will go up to the top of her cage and turn sideways into the light to digest her food.
Usually 20 minutes of sitting under here bulb she will start to gape.
I think you might be overreacting a little, but I would make sure he isnt making any cracking or popping sounds while breathing.
Better safe then sorry, right?
Here is a picture of my IR temp gun: