Can't use the urinal when next to someone. Is this psychological? It's a common symptom that men are unable to wee in public, for example in the urinals in a bar. This is sometimes called shy-bladder syndrome as far as I know.

Is this condition known to have physiological grounds, or is it a psychological issue?
Is this a psychological issue for me?


Depends: is there any other common factor that makes you unable to urinate? If not, then it's probably psychogenic.

It's very common. 


  Paruresis (Psychogenic Inhibition of Micturition): cognitive behavioral formulation and treatment
  
  Paruresis is a condition characterized by difficulty or inability to urinate in situations where others are present, or may soon be present. Despite knowledge that paruresis can significantly impact on occupational functioning, social functioning, and quality of life, there exists a paucity of research into effective treatments. Although cognitive conceptualizations have been advanced for other anxiety disorders, there has not been a comprehensive cognitive behavioral model of paruresis. This article presents a revised cognitive and behavioral conceptualization of paruresis, drawing on empirical evidence from other anxiety disorders. Using this conceptualization, a cognitive-behavioral intervention strategy is outlined, with clear targets for cognitive and behavioral strategies. 


Reference: Boschen, M. J. (2008). Paruresis (psychogenic inhibition of micturition): cognitive behavioral formulation and treatment. Depression and Anxiety, 25, 903-912. https://dx.doi.org/10.1002/da.20367/full