F10 stops the current event, so yeah, sounds like an event problem.

Make a new game and make a small island for your character to walk around on and see what happens.

If it's fine, make a new, blank map in your normal game and fill it with grass and stick the Party Starting Position on that map, and test. If it's good, then obviously there's an event on your normal starting map that is stuck in a loop or something. If it's slow again, you have a common event that's being called over and over.