If the device will not come on and stay on, you cannot factory reset it. If you cannot at least attempt a reset, it will need to be replaced either under extended warranty with T-Mobile or an insurance claim if you have handset protection. If neither, you'll need to replace it, but hold onto your paperwork and receipt. LG is being sued as we speak for V10 and G4 bootloop issues.
Take out the battery and let it sit until it cools down and try and see if it starts working like normal.