It is normal as long as he can move away from the heat if he want, and if you have set up a proper thermogradient where he can choose from a range of temperatures, rather than a "hot" spot and cold terrarrium.
Sometimes, especially after eating or drinking, lizards like to "cook" a bit and raise their core temperature and when doing this they will pant for a little while.
One reason I prefer thermogradients rather than hot spots with exact temperatures is because lizards are known to raise their body temperature higher than their preferred optimal temperature (POT) at times- sometimes for digestion, sometimes they even give themselves fever to fight infection.
So the answer to your question is- it depends on how you have set things up. If you have a thermogradient, then you can feel safe knowing he is doing what his instinct is telling him. If you have only a hot spot, you can't be so certain without experience if your hot spot is too warm or if he is simply doing what he feels a need to do...
If he does it often and when he is away from the heat- you need to be on the watch for a respiratory infection...