Why does my Vauxhall Astra engine rev too high when idling?

I recently noticed that my Vauxhall Astra's engine is revving too high when idling. The RPMs are constantly fluctuating and it's starting to worry me. What could be causing this and how can I fix it?

One possible cause for this issue could be a vacuum leak in the air intake system. Check all the hoses and connections for any tears or leaks. If you find any, replace them immediately.

Another potential cause could be a dirty or faulty idle air control valve. Try cleaning the valve with throttle body cleaner. If that doesn't work, you may need to replace it.

Low transmission fluid levels can also cause high revving in an automatic transmission. Check and top off the fluid if necessary.

It's also important to regularly maintain your car, including changing the air filter and spark plugs. If these components are dirty or worn out, it can affect engine performance.