What causes behavioural inhibition? There are obvious consequences that prevent people from behaving anti-socially or criminally. However there are many behaviours that are within the bounds of social norms, yet there seems to be some "invisible" force preventing people from letting go of inhibitions and acting spontaneously.  

What stops a person from doing something when they have the urge to do something spontaneous and random?

 I was in the process of answering another question when it was deleted; so decided to write my own question
The most common theory to date is that behavioural inhibition is developed from negative reinforcement.

Gray's biopsychological theory of personality 


  the Behavioural Inhibition System (BIS) and the Behavioural Activation
  System (BAS)  ../..  The BIS is thought to be related to sensitivity
  to punishment as well as avoidance motivation, while the BAS is
  thought to be related to sensitivity to reward as well as approach
  motivation.


There is some research that suggests that the BIS scale is better correlated with neuroticism and negative affectivity, rather than anxiety.


  The BIS scale was less correlated with anxiety and depression symptoms
  than are neuroticism and negative affectivity scales, probably because
  it is designed to measure predisposition to anxiety rather than the
  experience of anxiety. BIS scores were higher in females,...1


Brain Functions: Behavioral Inhibition, Behavioral Flexibility, and Cognitive Control

Discusses how we modify our behaviour and suggests that some behaviour is inhibited in an "auto-pilot" manner by the prefrontal cortex to free up our brain for more complex thought processes.


  We can inhibit our actions and behaviors while they are in progress,
  and we can also inhibit our emotions and memories. Different parts of
  the prefrontal cortex, at the very front of the brain, are used to
  interrupt these various types of behaviors or thoughts. Some theories
  even suggest that the role of the prefrontal cortex is to stop all
  ill-suited actions or thoughts, to leave room for more appropriate
  actions.


Overall, there are numerous studies showing a  link between anxiety and  experience of a fear based reward system  with behavioural inhibition.2

1 Using the BIS/BAS scales to measure behavioural inhibition and behavioural activation: Factor structure, validity and norms in a large community sample
A.F JormCorresponding author contact information, H Christensen, A.S Henderson, P.A Jacomb, A.E Korten, B Rodgers
NHMRC Psychiatric Epidemiology Research Centre, The Australian National University, Canberra 0200, Australia
http://dx.doi.org/10.1016/S0191-8869(98)00143-3

2 J Child Fam Stud. 2011 April; 20(2): 157–170.
Published online 2010 March 17. doi:  10.1007/s10826-010-9365-8 
PMCID: PMC3048305
Behavioral Inhibition as a Risk Factor for the Development of Childhood Anxiety Disorders: A Longitudinal Study
Peter Muris,corresponding author1 Anna M. L. van Brakel,2 Arnoud Arntz,2 and Erik Schouten2