Does equipting an artifact creature to itself cause a rules problem?

Equip is an activated ability that attaches an Equipment to a creature you control. However, CR rule 301.5b states that an Equipment cannot equip itself — specifically, the rules say a permanent cannot be attached to itself. This is a hard restriction, not just a suggestion.

When you activate an Equip ability, you must choose a target creature you control (CR 301.5c). If the Equipment is itself an artifact creature (like Cranial Plating on a creature body, or something like Blinkmoth Nexus animated), you still cannot choose itself as the target of its own Equip ability. Attempting to do so would be an illegal target selection.

This isn't a 'rules problem' in the sense of causing a game error or loop — the game simply doesn't allow you to make that choice in the first place. The targeting restriction prevents the situation from ever arising legally.

Example: You control a Nettlecyst, which is both an Equipment and an artifact creature. You activate its Equip ability. You must choose a different creature you control as the target — you cannot target Nettlecyst itself. If no other creature is available, the ability cannot be activated with a legal target.

Note that other effects (like Auras or forced attachment) also cannot attach a permanent to itself per CR 701.3d, which reinforces this as a universal rule across card types.