this is my blueprint, doing what you want (enhancement of 3rd person blueprint), hope that helps:
/edit:
don’t forget to set the “speed multiplier” variable value to 0.1, otherwise you will run until you pressed shift once 
this is my blueprint, doing what you want (enhancement of 3rd person blueprint), hope that helps:
/edit:
don’t forget to set the “speed multiplier” variable value to 0.1, otherwise you will run until you pressed shift once