When I turn on my car when the engine is warm it makes a screeching noise.

Hello, sounds like the drive belt could be slipping. If so, it would make a screeching noise as the engine is trying to drive the belt which in turn drives various accessories on the engine, such as the air conditioning compressor or alternator. Alternatively, you could have a concern with one of those components - air conditioning compressor, alternator to name 2 - or even a tensioner or idler pulley for the belt that could be binding or seizing. Hands on inspection is needed. https://repairpal.com/auto-repair-near-me