This is a case where there should be no problem, the two verbs have a clear different meaning and have a straightforward translation in English.

attendre quelque chose is to wait for something, s’attendre à quelque chose is to expect something

1. S’attendre à quelque chose: you are NOT sure of what you are waiting (expect, hope …).
2. Attendre quelque chose: you are sure of what you are waiting for (it will happen, it is just a matter of time)