5 yr old gaps for air at night. No swollen tonsils, no mouth breathing or snoring or any other symptoms of apnea. Can it be apnea? If so how to treat

Yes.....but. Sleep apnea can occur in childhood & is one of the few reasons tonsils/adenoids are removed in a 5yo. A visit to an ENT that works with kids can help you get started. If you can record the sounds of the kid sleeping it may be enough for the ENT to apply the SA label & plan treatment. It might be something else.