Low voltage track lighting flashing at low frequency
Because you have too much lighting load for the power supply (not transformer*) to cope with, so it is crowbar-ing. 

Reduce load.   This is a good time to think LED.  



* "Transformer" is a proper term for a very specific thing, which this is not.  Transformers are quite heavy and withstand short-term overload very well.  This weighs 6.4 oz. for 150W, and fails instantly at 100W. They can call it an A-10 Warthog if they please, but it's actually a switching power supply. As such it has a protective circuit (crowbar) which is tripping for whatever reason (defective? Misapplied? Loads you don't know about?) 

The RU mark is a good sign, but still it's only rated as an electronic component, it would need a UL mark to be legal for direct use in mains wiring.