Stop using it immediately. You are forcing the tool or using it outside its limits. Unplug the charger and remove the battery pack.
Likely causes: You are in too high a gear for the task. Speed 2 (1350 RPM) is for high-speed drilling. Speed 1 (350 RPM) is for high-torque screw driving. You changed speeds while the tool was running. Never do that. Let it stop first.
If that didn't work: Internal damage. Check for binding moving parts or a broken gear. Do not operate a tool that cannot be controlled with the switch. It is dangerous.
Heads up: Have your power tool serviced by a qualified repair person using only identical DEKO replacement parts. Do not attempt to repair it yourself.