Wattage of adapter for LED strip
Flickering is caused by the voltage conversion “driver” 
The driver sets the correct voltage and current level. The problem with today’s led’s Is they can be just about any voltage. For instance I have some 4’ strips that fire at ~40v but need ~60v for full brightness, so you really need to find the specs to get the proper driver for your lights. But yes flickering is a sign of the driver overheating and or starting to fail. I did look closer at your strips and they show 12v so then you would need a supply large enough in watts or amps at 12vdc to light them up.