si stia

is

→ si
phrase Rare #32,477
is Present subjunctive form used with reflexive verbs, often in subordinate clauses after expressions like think, wonder, or seem.
IT: Penso che Maria si stia preparando.
EN: I think Maria is getting ready.

Pensa che solo l'FBI si stia occupando di lui?

Do you think the FBI is the only one dealing with him?

— Prova a prendermi (2002)

Sembra che Tom si stia stancando.

It looks like Tom is getting tired.

Spero che Mary si stia comportando bene.

I hope Mary is behaving well.

Penso che il vento si stia indebolendo.

I think the wind is dying down.

Io penso che Tom si stia preparando.

I think Tom is getting ready.

Sembra che Tom si stia veramente divertendo.

Tom looks like he's really enjoying himself.

Peccato che si stia perdendo tutto questo.

It's a shame that all of this is being lost.

— Good Bye, Lenin! (2003)