One possible reason could be that Naruto is so focused on his goal of becoming Hokage. His mind is occupied with training and achieving power, so he seems cold to Sakura. He might not have the time or mental space to show her more warmth.
One reason could be that Naruto has grown weary of Sakura's unrequited love for Sasuke. He might feel like she's always focused on Sasuke and doesn't truly see him, Naruto. Another aspect could be that Sakura's constant nagging or her over - emotional outbursts have started to grate on Naruto over time. Maybe he's also tired of having to be the one to always cheer her up when Sasuke - related things go wrong.
It could be due to a new jutsu he's trying to master that has some side effects on his emotions. Maybe it's a powerful ice - based jutsu that's making him cold in nature as well.
One reason could be that Naruto is focused on his own goals like becoming Hokage and he might see Sakura's feelings or her actions as distractions. He has a lot on his plate and may not have the time or energy to deal with her in a warm way.
Maybe Sakura makes a decision that endangers herself or the team without consulting Naruto. In the world of Naruto, they are a team, and Naruto values his comrades. If Sakura does something reckless like that, it could make him angry.
One reason could be that Naruto has been through a lot and is emotionally drained. He might see Tsunade as a source of comfort and stability, so he calls her mom. His coldness could be a defense mechanism to hide his vulnerability. Another reason could be that he has seen how Tsunade cares for others in the village, and he subconsciously wants that kind of motherly love for himself.
One possible reason could be that Naruto realizes Sakura's unrequited love for Sasuke. He might feel tired of always being in a one - sided emotional situation with her. Another reason could be that Naruto has his own goals and growth to focus on. His journey to become Hokage and protect the village requires all his attention, leaving little room for his previous feelings for Sakura.
It could also be a part of some sort of training gone wrong. In the world of Naruto, they often engage in intense training. If Sakura and Naruto were sparring and Sakura pushed Naruto too far, perhaps by taunting him about his strength or his progress compared to Sasuke, Naruto might lose his temper and punch her.
One possible reason could be that Naruto has his own unrequited love for someone else and he is trying to distance himself from Sakura to avoid leading her on. For example, if he has deep feelings for Hinata, he might be cold towards Sakura to make his own feelings clear.
It could be related to some sort of external influence, like a curse or a dark chakra that has infected him. This could be slowly changing his personality from the warm - hearted Naruto we know to a cold - hearted version. For example, if there was a powerful enemy who placed a curse on him that targeted his emotions.
One possible reason could be that Sakura has finally grown tired of Sasuke's aloof and cold behavior towards her. She might have realized that she has been constantly chasing after him while getting little in return, so she decides to ignore him as a form of self - preservation.