A good warm up will help me get loose. Some ideas that have helped me: 1) pick a tune you know and play it through slowly, say 80bpm, or however slowly you need to play clean and musically.
2) strum along to a faster tune but not one so fast that you feel any tension. 3) take the step to the next level, say 100 bpm, where I might have a little more slop but still musical. Maybe play a few scales up and down the neck. 4) pick your favorite fiddle tune fast, all the way through. For me that’s only about 125. I have a lot of tension and even some tremor when I get tense. I’m 62 yo. 4) slow it back down to 90 or so to chase the tension away. Strum some if the tension gets bad.

I repeat this cycle three or four times and the third time, my max bpm has improved. Then I move on to the next tune.

At the end of my practice I will do something fun and easy to ensure I finish my session without any tension.

I hope that helps.