Instinct and anxiety both arrive fast and both feel like certainty, which is the entire difficulty.
There are a few tells. Instinct usually says one thing, once, quietly, and then stops. Anxiety says it again. And again, with variations, growing more detailed and more urgent the longer you sit with it.
Instinct also tends to be specific and small. Do not take this job. Call her back. Leave now. Anxiety is expansive and has opinions about the next eleven years.
If you cannot tell which one you are hearing, wait a day and see whether it is still there in the same shape. The real one usually is, still saying the same short thing.