- What, do you think, should I do first?
- What should I do, do you think?
Are the above sentences acceptable?
Best to combine both as - What do you think I should do (first)?
- What do you think I should do first? (This corrected form is acceptable as Alan has suggested)
- What should I do, do you think? (This sentence doesn’t make good sense; it also has two questions within itself, which is not grammatical)