[PyGame] Rectangle keeps teleporting?

[keyfive]

Hi, I am trying to make this cube move, but it just teleports when I let go of an arrow key. Please help!

import pygame

pygame.init()

# screen variables
sWidth = 1000
sHeight = 700

# colours
red = (255, 0, 0)
black = (0, 0, 0)
white = (255, 255, 255)

# Main mechanics
gDisplay = pygame.display.set_mode((sWidth, sHeight))
clock = pygame.time.Clock()
pygame.display.set_caption('Zube')




def gameStart():
    # Mechanics

    # Shapes and stuff
    playerStartingx = 64
    playerStartingy = sHeight - 100
    playerWidth = 60
    playerHeight = 60

    # Game Loop Variable
    playing = True

    while playing:
        for event in pygame.event.get():
            gDisplay.fill(white)
            pygame.draw.rect(gDisplay, red, [playerStartingx, playerStartingy, playerWidth, playerHeight], 0)
            if event.type == pygame.QUIT:
                pygame.quit()
                quit()
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    playerStartingx += -50

                elif event.key == pygame.K_RIGHT:
                    playerStartingx += 50

            if event.type == pygame.KEYUP:
                if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                    playerStartingx += 0

        pygame.display.update()
        clock.tick(60)


gameStart()