How do the characters' timelines interact in The Witcher TV series?

You are correct. There are three linear timelines: Yennefer's, Geralt's, and Ciri's, which start at different times but all coincide by the final two episodes.

Here is a timeline of the events depicted in the show:

Dates and relative position of events are taken from 3 sources:

In-show dialogue:

^{Ep.1 Ciri: You won your first battle at Hochebuz when you were my age.}

^{Ep.1 Renfri: Queen Calanthe of Cintra, she just won her first battle at Hochebuz.}

^{Ep.3 Tissaia: Princess Calanthe? Good luck with that. Word is she's even more stubborn than her father is.}

^{Note: This event occurring in 1210 contradicts the official timeline stating Calanthe was born in 1216.}

^{Ep.3-4 Yennefer: Instead, I've spent the last three decades cleaning up stupid political messes.}

^{Ep.4-5 Jaskier: What's it been, months? Years? What is time, anyway?}

^{Ep.2-5 Jaskier: Oh, are we not using "friend"? Yeah, sure. Let's just give it another decade.}

^{Ep.4-7 Geralt: I've been away twelve years and I'd planned on staying that way.}

^{Ep.7-8 Yurga: Cintran refugees, dead at least a week.}

^{Ep.8 Sabrina: It hasn't been two days yet. How is Nilfgaard's army here already?}

Showrunner's comments:

^{... Ciri's story takes place over two weeks, Yennefer's takes place over, you know, it's like 70 years. Geralt's takes place over 20 years.}

^{- Interview with tvguide.com}

^{Note that Geralt's timeline spanning 20 years does not match up with:}

<sup>1. Ep01 occurring shortly after the Battle of Hochebuz (which Calanthe won at Ciri's age ~13).
2. Pavetta being pregnant with Ciri at the Banquet at Cintra.
3. Ciri being ~13 in the present day.</sup>

^{A more reasonable timespan is around ~30 years, which coincides with the dates given in the books.}

Official Netflix timeline

1. https://www.witchernetflix.com/

2. ^{A quick crash course in the multiple timelines of The Witcher. #TheWitcher}

   

   ^{- NX - @NXOnNetflix, 10:52 AM - 7 Jan 2020}

Here's a chart I made recently. It briefly covers the events and their time of occurrence in the series.

Each episode of the first season of the show covers different stories from the first books by Andrzej Sapkowski.

For example:

Episode 1 - The End's Beginning is based on the 4th story from the book The Last Wish, called The Lesser Evil.

Episode 6 - Rare Species is based on the first story from the book Sword of Destiny, called The Bounds of Reason.

Even in the books, the stories are not linked chronologically and are set in different points along the timeline.

So yes, your deduction is accurate, the show jumps at multiple moments in time, as the main characters are introduced and to coincide with the original stories that each episode is based on.