We are traveling to St Moritz from Tirano for the day next summer. We would like to take a cable car ride once we get to the St Moritz station (we are traveling via the Bernina train) Can someone give me tips on how I can do this? I would like to cable car up to a mountain gave a late lunch and then go back to St Moritz for some shopping and then take a local train back to Tirano in the evening. Not sure what cable car I should take and where I get it from. Thanks!

It's not a cable car, but you might consider the funicular to Muottas Muragl. The views from that vantage point are breathtaking! I believe there's still a restaurant there.

These are the closest options:

https://www.mountains.ch/en/summer/

I suggest you catch a bus from the St Mortiz train station to the Sils-Segl-Frutschellas cable car, which is the next village past St Moritz and take it to the top. Lots of hikes up here and some lovely views. Also a restaurant or two.

We did this in 2021, and I wrote about the specifics in this trip report - just scroll to post #84

Swiss Sojourn

As you will obviously have no luggage deposit problem, you can theoretically go to all 7 viewpoints reachable by cableway.
IMO the best you can do is to go to Diavolezza, in front of the highest peaks and glaciers of Bernina.
The gondola to Diavolezza starts at Bernina Diavolezza railway station.
Bernina Express train 972 stops at Bernina Diavolezza.,
If you take another Bernina Express train, you will have to change at Alp Grum (a very scenic place where it's well worth to stop over!)
Trains from Bernina Diavolezza to Pontresina - St. Moritz every hr (40 min ride).

The other viewpoints are (IMO in this order of amenity):
Corvatsch: bus from St. Moritz plus gondola
Muottas Muragl: bus from Pontresina (every 30 min) to Punt Muragl plus rope railway
Piz Nair: rope railway plus gondola from St. Moritz
Furtschellas: bus from St. Moritz to Sils Maria plus gondola
Alp Languard: chairlift from Pontresina
Marguns: bus from Pontresina to Celerina Cresta Palace or train from St. Moritz to Celerina plus cabeway

Thank you so much for everyone s great advice. Really appreciate the advice and very informative information

First - check if your hotel gives engadin card for cable cards and busses + trains > you can check it on booking engadin ch
It's sometimes better to book a more expensive hotel and then save on cable cars.
You can go with it to Diavolezza and Piz Corvatsch (and that is doable in one day - done that but with a car )
Mentioned Muottas Muragl is cool place for panoramas, but it is not on the card. And... if you are staying there or going for a fancy dinner (the restaurant is super good) you will get a free ticket ;-) - I think after 18:00 for dinner )

Enjoy!

The OP is only visiting St Moritz as a day trip, so no hotel in the Engadine

It will be a very full day, too bad you can't stay even one night there. We traveled St. Moritz to Tirano early one Saturday morning on the regularly scheduled local train and it was empty, had the entire car to ourselves. No crowds, no tourists. It looks to be about 2-1/2 hours each way. Shopping in St. Moritz is upscale but nothing you would not find in other cities. Spend your limited time seeing cool stuff.