The next time it happens try to re-start it just after it shuts down.
If you have to wait a couple minutes before it restarts then odds are the motor is overheating and tripping it's internal thermal protect.
You then have to wait for the motor to cool off before it will reset and re-start.

Could be too much drag on the motor.
Try turning the drum in the correct direction it should turn fairly easily. You may want to try this on a couple other units to get a feel for it.

Could be the motor is c;logged solid with lint and not cooling properly.

Also check if there is a seal between the4 motor and blower. Sometimes if this is shot hot air is blown onto the motor instead of out the vent.

Lastly the motor may be on it's last legs and needs replacing.