The Goa'uld likely did not start out evil, but the detrimental effects of the Sarcophagus eventually led them down that path, roughly as stated in @Tyson's answer.

However, the Goa'uld have voluntary genetic memory - the Queens are able to pick and choose what memories and knowledge to pass to their offspring. Because most Queens are evil/ego-maniacal, that's the knowledge they pass on to infant Goa'uld - making the new symbiotes just as evil/ego-maniacal as their ancestors.

So yes, it is at some level the natural state of the Goa'uld to be evil as seen in the series. They are born with that state of mind, and as shown with Tanith, even as infants they will lie and deceive so that they can get their way.

It is unknown how or why Egeria's views of the Goa'uld were changed, and she is the only known symbiote to ever have such a change of heart.

The Tok'ra were created by Egeria through altering the genetic memories passed on, so they never had the Goa'uld mentality in the first place (which is one of the reasons they get angry if they're ever accidentally referred to as Goa'uld - they weren't born evil/ego-maniacal).

The Goa'uld likely did not start out evil, but the detrimental effects of the Sarcophagus eventually led them down that path, roughly as stated in @Tyson's answer.

However, the Goa'uld have voluntary genetic memory - the Queens are able to pick and choose what memories and knowledge to pass to their offspring. Because most Queens are evil/ego-maniacal, that's the knowledge they pass on to infant Goa'uld - making the new symbiotes just as evil/ego-maniacal as their ancestors.

So yes, it is at some level the natural state of the Goa'uld to be evil as seen in the series. They are born with that state of mind, and as shown with Tanith, even as infants they will lie and deceive so that they can get their way.

It is unknown how or why Egeria's views of the Goa'uld were changed, and she is the only known symbiote to ever have such a change of heart.

The Tok'ra were created by Egeria through altering the genetic memories passed on, so they never had the Goa'uld mentality in the first place (which is one of the reasons they get angry if they're ever accidentally referred to as Goa'uld - they weren't born evil/ego-maniacal).