Led light strip flashing
it's not a connection issue, those don't get better over time. your driver is failing because the capacitors in it are drying out. this will get worse sooner than later. 

As the LED strip warms, it uses more current. To supply more current, the driver increases its output voltage. When the voltage increases, a cap of a given capacity stores more energy. When the voltage catches up with demand, the flickering stops. Note that higher voltages tend to heat the capacitors and cause them to age even faster; a run-away cycle you're in the early stages of.