-나 싶다: I Wonder If — A Thought Half Held

-나 싶다 packages a half-held thought — I wonder if… / I sort of think….

Gloss: I wonder if — a thought you are half entertaining. 우리말샘 -나 「026」 lists -나 싶다 with other wonder/guess frames. 싶다 「002」: the speaker has the thought of the preceding content. Do not confuse with desire 싶다 「001」 in -고 싶다.

Soft inner wonder

감기가 오나 싶어요.
잘못했나 싶어요.
과로인가 싶어요.
효과가 있나 싶어요.
길이 막히나 싶어요.

Illness and self-check lines: you are entertaining a possibility, not announcing a verdict.

Forms

Shape	Note
-나 싶다	core
-었나 싶다	past-oriented wonder

Polite 싶어요.

Desire vs thought vs inference

Form	Lean
-고 싶다	want to
-나 싶다	half-held wonder
-나 보다	inference from signs
-을까	deliberative question

쉬고 싶어요.           desire
쉬나 싶어요.           I wonder if (someone) rests / if resting…
쉬나 봐요.             seems they rest (inference)

When to use it

Use -나 싶다 when the thought is tentative and internal.

Use -나 보다 when signs outside you support the guess.

Never swap in -고 싶다 when you meant wonder — that turns “I wonder if I’m sick” into “I want to be sick.”