w 210 acting weird

[Sylvester]

Hello i need help please, my 2000 mercedes e 320 a/c is doing something very weird, a/c delay on start up after sitting over night, turn the climate switch on, the blower comes on and compressor on, but blowing hot air, no evaporator noise, no freon sound, heres the weird part, if the climate switch left on over nignt, on start up it works great, also on cooler days while air on driving its blows cold air then hot air all of a sudden, but on 100 degree days the compressor stays on with no problems, gauges 40 psi low side, #3 vaule is 40 #4 is 40 #5 39 #7 17 sitting 11 driving, where do i start?? please help thank you very much.