LCD has strange characters when not lcd.clear() is sent

Using Arduino Displays
5

It happens with every code i use from the examples.

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(20,2);
 }

void loop() {
  // set the cursor to (0,0):
  lcd.setCursor(0, 0);
  // print from 0 to 9:
  for (int thisChar = 0; thisChar < 10; thisChar++) {
   lcd.print(thisChar);
   delay(500);
  }

  // set the cursor to (16,1):
  lcd.setCursor(16,1);
  // set the display to automatically scroll:
  lcd.autoscroll();
  // print from 0 to 9:
  for (int thisChar = 0; thisChar < 10; thisChar++) {
    lcd.print(thisChar);
    delay(500);
  }
  // turn off automatic scrolling
  lcd.noAutoscroll();
  
  // clear screen for the next loop:
  lcd.clear();
}

when i send this code to the arduino, i get rubish.
When i insert lcd.clear(); after lcd.begin(20,2); then it is al working.
This happend with every code

I spend hours to this, and i don't understand it.