ok.
Fixed : was not a wire problem.
The only thing I've made is to insert a 0.22uF capacitor between pin 1 (reset) and GND.
After that situation is (quite) stable.
Thanks anyway for helping me. 
ok.
Fixed : was not a wire problem.
The only thing I've made is to insert a 0.22uF capacitor between pin 1 (reset) and GND.
After that situation is (quite) stable.
Thanks anyway for helping me.