Shifting is the term we use to name the process of moving the left hand from one position on the cello to another position. Looking at the fingerboard provides neither clue or guidance. When people are performing, they may not wish to look at the audience because it is distracting or makes them nervous, so I would never presume they look in the direction of the fingerboard because they need to see their shifts. If they had to look in order to shift, they probably wouldn’t be on stage…
Shifting is about timing and balance. When we play a note, the weight of the arm should be balanced so that the forearm rotates slightly in the direction of the finger that is playing, and simultaneously the elbow must be at an angle such that this is possible. This allows the weight of the arm and hand to be applied effectively on the finger that is playing. When shifting to higher positions on any string, you must raise the elbow slightly in anticipation of the new position, as the shape of the cello requires this once we approach the body of the instrument. Once the elbow is in position for the new position, it is simply a matter of opening the elbow a bit to move the hand into the new position. Anticipation by definition means that these things take place before the change in position. To fully anticipate an upward shift, imagine first that the note preceding the new position is divided in half (in your mind). As you begin the note before the shift begins, raise the elbow to the plane it needs to be on in the new position (this releases some tension in the hand and weight from the finger). Halfway through the note before the new position, begin to move the hand at such a speed that the hand arrives at the new note in time for the new note to sound. This needs to be practiced very slowly with a metronome until the brain understands the timing, and the body is well coordinated. If you want to hear the shift, you keep the bow at the same speed and pressure throughout the shift (it is useful to do this until you have the timing and the coordination well trained), and if you do not want to hear the shift, you release the pressure of the bow and slow it down during the shift. Varying this combination of speed and pressure with the bow is how we make variety in our shifts. Once mastered, there are variations in this (such as the delayed shift, where the slide happens at the time the new note is to sound and the new note is slightly delayed as a result. A great pianist will play a melodic note slightly late to everything else as a way to make an espressivo accent. We, of course, can make an espressivo accent by shaping a note with the bow, but I hope you understand how the delayed shift and this piano technique have similar expressive purposes. A good way to practice shifting is to play very slow scales with a metronome set for 2 beats for each note you play (that way the timing of the shift can be disciplined).
Letting go of fear important; shifting is like walking, it is all about balance and pacing. We all can walk (absent disability), and we can all shift with ease, so there is no cause for trepidation.
Many of the great teachers (Rose, Starker, Parisot, Janigro, etc.) distill the principles of playing down to a very basic level. Whether your hand is small or large isn’t relevant, really; the balance of the weight of the arm as applied through the discrete rotation of the forearm, in both the left hand and the right (with somewhat different involvement of the muscles of the back regarding each). For the left hand, rotation equals release of the initial finger’s “pressure” and the application of it to the new finger, the weight of the arm/hand being equal upon each finger in its turn. In the case where the hand is small, rotating the hand reduces the “stretch” in melodic (non-double-stopped) intervals, just as it does for a larger hand, the difference being the amount of rotation and the anticipated distance between the fingers that is required. Moving from one position to another is also a matter of anticipation (minimizing motions that occur during the movement of the hand from one position to another by creating the new position as much as possible in anticipation of the shift). The balance of the hand in the position before the upward shift (typically favoring either the 4th or 3rd finger) is different than that after the shift (typically the 1st finger). Starker and Parisot taught/teach a clockwise-circular motion of the left elbow in anticipation of the shift, which naturally shifts the balance of the hand. I personally feel that this is a good way to get the concept of shifting balance well understood, but it is important that one not introduce too much extraneous motion into the shifting process itself once understood and accomplished, as less extraneous motion equals less likelihood of error.