What if your motor silent on key turn doesn't start on many attempts

You turn the key but the motor is silent Sometimes you try once or twice nothing. No sound. Suddenly it starts. Same with 7 times. It could be related to the minus black grounding wire of the battery. Unscrew it from the chassis clean the bolt and wire with some alcohol. Put it back. Voilà. Could be also also battery but that will give you a sound on keyturn usually