I've just installed a set of five 20w low voltage halogen spotlights in the bathroom. Everything seemed to be in order until tonight when I turned the switch on the lights took literally 5-10 seconds to come on. I had noticed a slight delay when I installed them but it was only a second or two, I just put it down to the transformer kicking in. Tonight the lights seemed to be trying to illuminate then dimming then trying again before eventually reaching full brightness. When I turned them off again I turned them straight back on and they came on with the 'normal' second or two delay. What could cause them to be slow starting intermittently??