Static electricity at analog pins

Hello, I'm using Arduino Mega 2560 and I have noticed something weird, I tried to repeatedly check the input electricity flow from the analog pin A0 by this line "Serial.println(analogRead(A0));" and it showed values between 355 to 365. Then I have connected a wire to the pin that was connected to nothing and it showed the same range of values, but when I touched the wire with my hand it jumped to 0 instantly (as expected). My theory is that there is a static electricity at the analog pins and as soon as I touched the wire the electricity jumped to my hand and showed 0.

What is your opinion about that? and do you have any suggestions on how to keep the values at 0 like they should be?

There is no reason for the input to read 0 as a default. Think of the attached cable as an antenna. It will always catch something out of the air. This is also the case even if the "antenna" is just the bare IC pin w/o cable. Just don't let the input unconnected if you want a meaningful reading

Google "floating pin"

Delta_G:
Google “floating pin”

Thank you very much for the help, I did not try to do this myself yet but I have found this useful video: Floating Pins, Pull-Up Resistors and Arduino - YouTube