Hello,
I've just booked train tickets for Munich to Vienna on DB. I booked first class, but there were no seat reservations available. Does this mean there is a chance I will have to stand on the train? Or does it just mean that I'll have a first class seat but I won't know where to sit ahead of time?
If there is no seat reservation mentioned on the ticket such as "Wagen xx, Sitz xx" (xx = numbers) then there is no seat reserved.
If the train is filled up standing is the only alternative if the few pre-reserved seats for loyalty customers (Bahnbonus Gold and Platin seats) are not filled up.
To erase all "if"s above better try to book a seat separately the same way you bought the ticket. It's free for first class passengers. There is a switch in the user interface to buy seat reservation only. More info about seat reservation.
It's free for first class passengers.
That's true only if you book your seat together with a flex price ticket.
You can still can try to book seats: On the DB website search for your booked connection and click on "book seat only".
Unfortunately, you will have to pay extra for a separate seat reservation, even if you already have a Flex Price ticket