MySQL doesn't start without sudo cmnd use for run sudo MySQL

mysql @localhost error

First, connect in sudo mysql

sudo mysql -u root
Check your accounts present in your db

SELECT User,Host FROM mysql.user;
+------------------+-----------+
| User             | Host      |
+------------------+-----------+
| admin            | localhost |
| debian-sys-maint | localhost |
| magento_user     | localhost |
| mysql.sys        | localhost |
| root             | localhost |
Delete current root@localhost account

mysql> DROP USER 'root'@'localhost';
Query OK, 0 rows affected (0,00 sec)
Recreate your user

mysql> CREATE USER 'root'@'%' IDENTIFIED BY '';
Query OK, 0 rows affected (0,00 sec)
Give permissions to your user (don't forget to flush privileges)

mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;
Query OK, 0 rows affected (0,00 sec)

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0,01 sec)
Exit MySQL and try to reconnect without sudo.