apoltronarse

Reflexive-only in practice: to settle comfortably into an armchair (poltrona) and, by extension, to become lazy or complacent, often about someone who's grown too comfortable in a position of power or ease.

• Se apoltronó en el sofá y no se movió en toda la tarde. — He sank into the sofa and didn't move all afternoon.
• Algunos políticos se apoltronan una vez que llegan al poder. — Some politicians grow complacent once they reach power.
• No te apoltrones, todavía hay trabajo que hacer. — Don't get comfortable, there's still work to do.

Using this for simple physical sitting — it carries a built-in judgment of laziness or complacency, unlike neutral sentarse (to sit down).

Often confused with acomodarse.