My A/C works sometimes

Hello,

It sounds like you could have a faulty clutch for the A/C compressor. It can also be the pressure switch for the A/C system.
If you have a faulty switch it can provide incorrect data and the compressor will not engage. The switch is located right behind the front grille.

https://www.2carpros.com/articles/how-a-car-air-conditioner-works

If the compressor clutch does not engage the air will not be cold. A clutch can go bad due to internal failure.
You can do visual inspection of the clutch, check the plated parts of the pressure plate for color changes, peeling or other damage. If there is damage, replace the clutch set.

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.