No, not every scientific method begin with an observation. ... And in scientific method before observation, first we predict (what will happen in the experiment). after prediction we observe. Prediction is known as hypothesis.

Does every scientific method begin with observation explain?

It is not a rule that every scientific method should start with observing, sometimes you can predict the result of an experiment then observe if your prediction is right or wrong.

Does the scientific method require observation?

A scientific process or scientific method requires observations of nature and formulating and testing the hypothesis.