Emotions drive creativity and connection AND emotions can be unpredictable, wild, and inexplicable. Getting stuck "in our heads" is a safe, logical place to be. This "thinking tactic" is totally handy at times--taking the emotion out of things and thinking facts-only; but in improvisation, where facts can be scarce, your brain gets "stuck."
What to do?
I have every confidence in your capability to courageously experiment and explore new tactics. One that I see working with my students is taking a pause and connecting with how you feel.
Sit with how you feel; where you feel it; how you're breathing it.
If you don't feel anything, take a guess. Pick an emotion and pretend with your body, breathing, voice.
You don't need to get out of your head. Your head means well. It just likes to forget about those pesky, unpredictable, volatile emotions that also happen to serve as powerful creative rocket fuel.