Why is pygame unstable?

Question

Python

When I change the time delay , the player starts to move slower or faster. But that's okay, he trembles and somehow jerks around. What to do?

import pygame

pygame.init();
win = pygame.display.set_mode((320,320));
pygame.display.set_caption("Game")

x = 144
y = 144
width = 32
height = 32
speed = 5

run = True

while run:
  pygame.time.delay(20)
  for event in pygame.event.get():
    if event.type == pygame.QUIT:
      run = False
  keys = pygame.key.get_pressed()
  if keys[pygame.K_UP]:
    y-=speed
  if keys[pygame.K_LEFT]:
    x-=speed
  if keys[pygame.K_RIGHT]:
    x+=speed
  if keys[pygame.K_DOWN]:
    y+=speed
  win.fill((0,0,0))
  pygame.draw.rect(win, (0,0,255), (x,y,width,height))
  pygame.display.update()	
pygame.quit()