What helped you transition baby to a cot?

My baby is 15 weeks old and outgrown her bassinet. Tonight is night number four of sleeping in her cot. Out of the last three nights the first was the only good one where she slept through to her next feed, fed and went back to sleep til her next feed. The last two nights she has woken about half an hour to an hour after I've put her down. So I'm just wondering if any of you mamas who've already transitioned to cot or are currently doing so have any tips? She sleeps swaddled btw as she startles otherwise.