There is no G35 in 2001, therefore you must have a 2003 instead, with the 3.5LV6.
Disconnecting the battery will NOT reset your radio, and may affect the operation of your vehicle. Below is the only test for the audio controller.
Self Diagnosis Function For A/C and Audio Controller
Perform self-diagnosis for A/C and audio controller, as well as audio unit, and display results on A/C and controller display.
As for mode 2-4, items are displayed with a 10-digit display.
OPERATION PROCEDURE
1)Within 5 seconds after turning ignition switch from OFF to ON, press function switches 1 and 6 simultaneously, and hold them for 5 seconds or more.
2)When self-diagnosis is actuated, all segments on display are displayed and mode 1 is active
3) Each time AUDIO switch is pressed, diagnosis mode switches. (MODE 2 to MODE 3 to MODE 4 to MODE 1)
4)Turn ignition switch from ON to OFF, or press function switches 1 and 6 simultaneously and hold them for 5 seconds or more to complete the self-diagnosis
MODE 1
Each time TUNE switch is pressed, segment display status is switched and missing segment is checked.
MODE 2
Each time TUNE switch is pressed, versions of A/C and audio controller, as well as audio unit are displayed.
MODE 3
Each time each switch is pressed, key codes of each switch are displayed and input status of each switch is checked.
CAUTION: When AUDIO switch can switch modes, it is judged normal.
MODE 4
Each time TUNE switch is pressed, error records of A/C and audio controller, as well as audio unit are displayed.
NOTE: Disc difference indicates special shaped disc or damaged disc.
Erase history of errors
Erase history of errors, press function switches 4 and 6 simultaneously in mode 4, and hold them for 5 seconds or more.
Erase results of error records are displayed on display.
ONLY PERFORM THESE DIAGNOSTICS IF YOU KNOW WHAT YOU ARE DOING
Used out of context they may not be useful , and or lead to a solution by you
Most likely your radio will need checked while in the vehicle with a diagnostic computer, and or may need to be replaced with a refurbished audio unit from an authorized service center.
Usually CD players do not like heat, they will goof up more on hot days, and than cool. If you have discs stuck in the unit most likely it will need replaced, or sent out to be repaired either of which will not be cheap.