My ebike motor powers down randomly

Can anyone help me identify what’s going on? As I’m riding, the mid drive motor on my E bike sometimes starts making a whirring noise and then loses power. The console and lights remains on but the motor doesn’t give any more assist. When I turn the power off and back on, it works again. Does anyone know if this is more likely to be a battery issue or a motor issue?

I’ve taken it into a mechanic that specializes in E bikes already, but the business was brand new and, based on my discussions with them, I didn’t trust that they knew what they were talking about. I feel like, when it comes to E bike repair, it’s the wild west out there.