The research phase is a must in almost any project. Its length and scope will vary (depending on the project size) but it’s essential that you do some amount of your own research in order to get a clearer target picture for the whole team. Regardless of whether workshops are held before or after, the client’s goals often need to be concretisized into a backlog of epics and tasks to complete during the project. Not to mention that this is usually when you have time to find out more about the end user’s needs.
This is also where we establish guiding principles, values and priorities for the design work. Your end goal with this phase is to establish a solid idea on which you can continue to build.
The research phase and the workshop phase often go hand in hand and will sometimes happen more or less intermittently. For example, sometimes you will need to do research before any workshops can be held. You will probably have to supplement that research before you move on to wireframing but if there's very little background information from the start it can be useful to do some research before hand. Maybe even before estimating.