I have a one year old rescue named Nacho, he was always so friendly and loved being pet and handled by anyone. When he was little (about 3 months old) for about 4 months I had another kitten and they would play together for hours 0 aggression, just fun. (the other kitten sadly passed away of leukemia) and nacho has since been alone and a house cat. He gets plenty of love and attention. About 3 months ago I started taking him to the groomer (only 2x) to get his nails trimmed because I was scared to do it myself and that's when I realized he developed a fear of driving in the car, when he used to love it. On top of that I had a few guests over the past 3 months and he would hiss and try to scratch and bite them and today the same thing with the vet. When he used to go to the vet everyone always held him and complimented how calm and loving he was. Hes scheduled for a neutering since hes not but i've read so many articles that say its not hormonal and its behavioral and neutering him wont help (im getting him neutered anyway cuz he needs it but still). I want to assume he started getting aggressive because of however the groomers were handling him and he'd lost trust with strangers? but how the heck do i fix this!? He used to be such a social and loving cat (he still is with my family but strangers is a no) help please!