Overcumbered
If your character is overencumbered in Starfield, they will still move normally, however, your character will begin to use more oxygen, regardless if you are running normally and not sprinting. This will result in your character eventually losing health over time. In order to prevent this, you must drop items until you are no longer encumbered.
Character Walking Slowly
If your character is moving slowly with a walking animation, please make sure that you have the option "Toggle Always-Run" toggled ON. You can press [Caps Lock] on Keyboard to "Toggle Always-Run" ON or OFF.