Hi Acetronic2,
thanks for your reply and sorry for my late to reply to you.
There's no adc problem because if i use a trimmer i can read very low voltage and sure i use a 10bit conversion.
In anyway i have partially resolved the issue with more readings(64) for time and now i get more stable reading, but at low temperature the LM35 stay very unprecise.
I have see that if i unpower the circuit(and lm35 too) and after few second repower it i will get 2 degree different read when the enviroment temperature is below 9 degree.
So i think i need to change temperature probe because lm35 is very unsatisfactory for me for this aplication.