Car engine performance is sporadic

I have a 2000 Holden (Opel) Astra.

The performance of it is sporadic.

The driveway I live on is a hill, and a couple of days ago, reversing it seems like the engine is stalling and it requires a big rev of the engine.

A couple of days later, and it’s fine.

What’s likely going on here? Air filter? Oil? Something else?