Can a person go back and forth from being schizoid to borderline personality disorder? are these two related and is it possible to be displaying both?

Unlikely: One is flamboyant and filled with interpersonal drama. The other is silent and withdrawn. If you are seeing both, personally i would consider a dissociative disorder as a highly likely explanation.

You can have both: They are not mutually exclusive. It is entirely possible for a person to have both conditions. The behavior and symptoms associated with borderline may appear only under distress (e.g., when the person fears rejection or abandonment). When things are stable, the person may then look schizoid. These are both complicated diagnoses-- a professional evaluation is in order.

Traits: You may not have a diagnosable personality disorder. You can, however, exhibit traits from one or more personality disorders even if full criteria is not met for a diagnosis. You may also have a concurrent mental illness and a personality disorder. Many possibilities, only your psychologist or psychiatrist can positively diagnose you.