IEEE journals are not monolithic and timing and handling differ. As a first step, someone looks at the paper, often a graduate student, to find candidates for a desk reject or to ask submitters to follow the style guidelines. Then the editor looks at the paper and assigns an AE who then tries to find reviewers. Sometimes AE beg to be let off because they are experiencing a busy time. There is a deadline given to the AE, but since finding reviewers is difficult, this deadline is often not met. There are often time lags between status changes on the website and the actual workflow.
The delay you observed can be caused by many different causes and even someone with intimate knowledge of the workflow at the journal could only speculate. For example, most people involved might be traveling to the same big conference or there might have been a random surge in submissions.
In any case, you submitted, and now you get to wait. IEEE from my experience is very careful at handling quality submissions and cases where a paper gets lost in the process for some time are extremely rare. There are mechanisms in place to find these cases and a reasonable time to a decision is a goal of the editing process. If you stay in academia, you will get used to waiting for a decision.