In our german forum, there is a discussion about the translation of this quote in the rulebook:

If the offense has no encounter cards (attacks, negotiates, or
morphs) at the start of his or her turn, the offense must play (if
possible) or discard any non-encounter cards, draw eight new
cards, and continue his or her turn.

Does this mean, that i HAVE TO play any non-encounter cards if I can play them and can only swap my cards if there are no cards left that I can play?

Or can I freely chose to swap my cards, even if I could play some of them?

You do not have to play them. You have to either play them or discard them. For example, you would not want to play Mobius Tubes if you had no ships in the warp.

For each card you have in your hand, you have to decide whether to play it (if it is possible to be played at the beginning of a turn) or discard it. Once you have done that with all of your cards, you get a new eight-card hand, keeping none of the cards you had before your turn started.

Oha.. you must discard your whole hand every end of your turn? didn't understood it this way...

No, you never have to discard your cards at the end of your turn unless there is a power or card that forces you to do so.

I was talking about only the situation you asked about: what to do when you start your turn with no encounter cards. I should have made that clear.

Okay, now I understood. Thx for the answers