I'm working with quarterly time series data. The series does not have a trend but fluctuates around more or less a constant mean. I observe weak seasonality such that the values are somewhat lower on average in the first and third quarters compared to the remaining two quarters.
My task is to work with a seasonally-adjusted series. I thought about transforming the series into a 4-quarter moving average series. Would this be a good way of accounting for seasonality? Any other suggestions?