If you're thinking of watching this series because of romance, then forget it. It's about a hospital basically run by a medical phenomena.
This series should be watched from S1, then S2 before watching S3. Each season brings something to the table from the previous one so I wouldn't skip any.
This series is the best medical drama I've ever seen. The procedures are intricate. It's basically about medicine ruling over politics and the person who drives that passion for saving people's lives which he calls romantic.
I'm not sure what to expect for S3 after watching the 1st 2 episodes but from seeing the previews of next episode, I'm not sure if this season is about the medical procedures or more on the interactions of the hospital staff. Time will tell.
Anyway the first two seasons are on Netflix and this third season is available on Disney plus (Netflix loss).
It's the same situation with Taxi Driver. Another great show, shown on Netflix but saw that S2 is on Viki which is a pain as Viki app can't be installed on Tv