You really need to check the crabitat temperatures and humidity first.
The lamps can rob the tank of needed humidity, the pad heaters on one end of the tank is best.
Hermies will dig seemingly no reason, to destress or molt is common, cooling off or warming up, or getting humidity are others.
Some simply dig, often coming up at night for a bite and drink, or to play and explore.
Beyond all that, sounds quite normal to me.
They can dig and be gone for weeks when they molt.