I think that the best way is a conversation with native speaker. During the dialog with some magical way skills come back to you))) Of course you need more than one lesson, but it worth.

Today I’m going to take my first class after a 1-year and half gap and I feel the same as you: my tongue seems to be stuck in my mouth. Tonight, I will come back here to tell how like I felt after this first class.

I'm currently learning Spanish and Esperanto, so I can relate on that level (although I am an English teacher/community tutor as well). I would say the best thing you can do is start at a low and fun level - reignite your passion most importantly. Watch a movie or some series, some Youtube videos. Go over some of your old notes and vocabulary sheets, maybe try and read and article or a book and see how much understanding and vocabulary you have attained. Learning apps are a really great way to stay consistent and measure how far you have fallen back. Once you feel a little more confident and ready to re-test your skills, book a lesson or a have a conversation with an English speaking friend. Keep building on to your learning experience in an organic way.

Last thing I would say is trust yourself and your own abilities, nobody knows better about what you need as a learner than yourself. Happy learning :)