It's because of your loop.
It would be easier if you show a screenshot of your event, because there's a lot of important information that you haven't included. Use Alt + PrintScreen to capture just the event window (no map/background). If you have multiple event pages, we'll sometimes want to see several of them.
Do you want the player to keep gaining HP while they stand on that spot? So they could just move there then go and have some lunch and be fully restored by the time they get back? In that case you'll want to use some kind of parallel process event to do the wait 5 frames and add HP. So the event they stand on might just turn on a self switch on the Player Touch page. Then add another page conditioned by the self switch that is set to parallel process. This will check to see if the player is still standing on that spot (using variables to get the player's position, then comparing them to the event's position), and if the player has moved, it will turn the self switch off again. But if the player is still standing there, it'll add 5hp and wait. Don't put a loop in this event - the parallel process trigger will cause it to loop by default.
