Insert Row With Foreign Key Equal to ID - Circular Reference
Solution 1:

Make the event_id nullable.

ALTER TABLE events
  MODIFY COLUMN event_id int unsigned NULL ;


This will allow you to insert rows which reference nothing (NULL): 

INSERT INTO events
  (user_id, event_id, title)
VALUES
  (a_valid_user_id, NULL, 'test event 1') ;


And to see events without a "parent" event:

SELECT *
FROM events
WHERE event_id IS NULL ;


Test at SQL-Fiddle-1



(Parenthesis)

Unless you have some braindead ORM that requires all tables to have a column named id, it's better to have names that describe what they represent. I'd rename id to event_id and event_id to parent_event_id:

CREATE TABLE events (
  event_id int(10) unsigned NOT NULL AUTO_INCREMENT,
  user_id int(10) unsigned NOT NULL,
  parent_event_id int(10) unsigned NULL,
  title varchar(200) NOT NULL,
  PRIMARY KEY (event_id),
  --- ...
) ;