Learn Turkish: Bu bana sadece bir önsezi gibi geliyor. - This seems to me like just a hunch.

The phrase gibi gelmek literally translates to 'to come like [something].' Because the impression 'comes to' you, the person experiencing the feeling must be in the dative case (bana, sana, ona, etc.). It carries the nuance of 'it strikes me as' or 'it seems to me.'

Could I replace bana ... gibi geliyor with bence?

Not in the exact same sentence. Bence means 'in my opinion,' and it doesn't pair well with the verb gelmek here. You could drop the verb entirely and say Bence bu sadece bir önsezi (In my opinion, this is just a hunch), but if you use the structure for 'it seems,' you must use the dative pronoun bana.

Why is sadece bir placed where it is, rather than before bana?

In Turkish, modifiers stay close to what they modify. Sadece bir modifies önsezi (just a hunch), so they form a single block of meaning. The standard order here is [Subject] + [Dative pronoun] + [Noun block] + gibi geliyor. Keeping sadece bir önsezi together right before gibi ensures the sentence clearly means 'seems like just a hunch.'

What is the literal breakdown of the word önsezi?