shower keeps stoping?

Is it an electric shower? If so, when the shower is switched on and it only flows for a second or two, the problem could be a faulty on/off switch. Try holding the button in, when you turn it on, if it continues to work and the water is it's normal temperature, the switch is "banjoed".
or
The safety cut out may be the problem. This stops the heating element on the unit becoming too hot and in danger of burning out if there is low water pressure/flow.
or
SWITCH OFF THE ELECTRIC and remove the cover. Check for any loose connections or look for blackened or melted wiring. Even check with your nose to check if there is a smell of burning.
Try these options, but if any repairs are required call the experts in !!!!!
WITH WATER & ELECTRIC, DON'T FIDDLE,
OR YOU'LL COOK ALL THE WAY TO THE MIDDLE.......

Davy Mac
March 2009