Does When Move ability resolve instantly?

No, "When I move" abilities do not resolve instantly.

According to the rules and FAQs regarding movement:

• Movement itself is instantaneous: Per Rule 424.3, moving is instantaneous and does not use the chain.
• "When I move" triggers create a chain: Per the FAQ, "When I move" is a triggered ability that is placed on the chain. This gives players an opportunity to react to the trigger once it is on the chain.
• Resolution: Because these triggers are placed on the chain, they must resolve according to standard chain resolution rules (LIFO - Last In, First Out). They do not resolve instantly at the moment the move occurs.

Additionally, per the FAQ regarding "When I move" triggers and combat:

• These triggers are finalized during the cleanup phase after a move.
• If a move triggers an ability, the chain must be empty before any staged Showdown or Combat can begin.