gut (feeling|reaction)

a belief that is strong, yet without any explainable reason

The idiom "gut feeling" is believed to have originated in the 19th century and refers to an instinctive or intuitive belief or impression that is not based on conscious reasoning or evidence. It is used to suggest that the speaker has a deep-seated sense or hunch about something, often without being able to fully explain or justify it.

I had a gut feeling that the job interview was going well, and I was right.
My gut reaction to the new restaurant was that it was overpriced and overrated.
The detective had a gut feeling that the suspect was guilty, even though there was no concrete evidence
The athlete trusted her gut feeling when it came to making game-time decisions.
The investor made a gut decision to invest in the start-up, even though it was a risky venture.