DIAGNOSIS The motor is starving for air. The most likely cause is a clog in the hose or the brushroll chamber.
FIX Detach the hose from the pod. Remove the dust cup and filter. Look through the hose for debris. Check the opening at the base of the pod where the hose connects. Use a broom handle or similar long object to gently push any clog out.
IF THAT DIDN'T WORK Remove the brushroll. Check for a massive hair wrap. Also inspect the clear plastic elbow under the pod that leads to the hose. Hair and string can pack in there.
HEADS UP Never run the vacuum with a clog for more than a few seconds. The motor cools itself with airflow. A prolonged clog will overheat and kill the motor.