Ok, so that works out to 2 hours 14 minutes from scheduled landing to departure from Munich Hbf.
If your flight is on time, you allow an hour for immigration, baggage claim, and customs, and 45 minutes for the S-Bahn ride, that gives you 10 minutes to move with luggage to/from the train platforms on each end and 9 minutes to wait for the next S-Bahn. That's conceivably possible, if all goes reasonably well. A small flight delay, extra-long lines at immigration (especially if you're not an EU citizen), or even just arriving as an S-Bahn leaves could be enough to miss it. Your flight could arrive early, you could breeze through immigration, and you could make it no problem. I wouldn't want to rely on it, especially if I'd be out the cost of the ticket if I don't make it. You'd have to weigh the consequences of missing your train to decide.
Depending on the costs involved, it might make sense to buy a flexible train ticket. You can look on Bahn.de or use the app to find the next set of connections to Vienna after you get out of customs. Or just plan on taking a later train.