Hola Mark, 

To ask someone in Spanish, " Do you have a (any) problem?", or "Do you have any problems?"  the following is used for both a singular problem or more than one problem:

Formal:  ¿Tiene algún problema? 

Informal: ¿Tienes algún problema? 

Before any singular masculine noun, instead of using 'alguno' we use 'algún'.  Problema is a masculine noun, el problema= the problem, un problema= a problem, algún problema= any problem/s. 

If you wanted to say "some problems" you would use "algunos problemas". 

I hope this makes sense and that it helps. I'm sure Inma or one of the team will confirm or better explain if needed. 

Saludos 

Clara 

Thank you, I hadn't realized problema was masculine with that sneaky terminal a!

You're welcome Mark. I often have to remind myself that problema is masculine! As you say it's a sneaky one! :))