Headlights flashes sometimes when I drive

There are two things to look for, (three if computer controls are part of the circuit). In the past, head light switches have had internal auto-resetting circuit breakers in case a wire became shorted. Often the contacts for that circuit breaker became pitted or arced, and that caused them to overheat to the point the breaker would trip, then quickly reset. Those built-in circuit breakers caused much more trouble than they prevented. The clue typically was the flickering occurred more often when using the high beams because they draw more current. On most older cars, arcing of the circuit breaker also caused the tail lights and dash back-lights to flicker. If you're fortunate enough to see that, the cause of the problem has to be before the dimmer switch.

Another common cause is burned terminals at the head light switch or at the dimmer switch. You need to look at the connectors, and if you find one or two blackened terminals, that switch must be replaced, and the black terminals must be cut out of the connector, then they are replaced with individual terminals that can be plugged in separately. When terminals overheat, you will also find about four inches of their wire is hardened. That must be cut off too because solder wont stick to that. Splice in new wire, crimp the new terminals on, but solder them too. Seal the splices with heat-shrink tubing. Never use electrical tape in a car because it will unravel into a gooey mess on a hot day.

If you cannot find a bad switch or connector terminal, we will need to connect something that lets you see where the problem is occurring. Typically we would connect a test light on the wire that goes from the head light switch to the dimmer switch. If the test light flickers when the head lights flicker, the cause of the problem is before that point. If the test light does not flicker, move it further down the line, then watch what happens the next time the problem occurs.

Some newer cars use relays to turn the head lights on. Those will be in the under-hood fuse box. If you have those, swap the head light relay(s) with one of the other ones like it. If the relay was the cause, the lights will no longer flicker.

Are the lights flashing on when they are supposed to be off, or flashing off when they're supposed to be on?

You didn't list a model so I can only offer some general suggestions. I think I would be looking at the multi-function switch, (turn signal switch), if that is where your dimmer switch is built into. Given that rough roads is a contributing factor, my suspicion is there is an intermittent connection, either at a connector, or inside the dimmer switch assembly.

The way I would approach this on my own vehicle, where time is not an issue, would be once I knew if it was the low beams, high beams, or both with the problem, I'd connect a voltmeter to a wire in that circuit, then watch what happens to the voltage on that wire when the flashing occurred. If the voltage remains steady, the defect is further down the line, so I'd move the meter's probe to the next test point. If the voltage changed while the problem occurred, the defect is before that point, so I'd move the meter to the previous test point in the circuit. That can be a time-consuming way to locate the cause, but it avoids wasting money on parts that aren't needed.

"2011" is the year your vehicle was built. Kia made 8 different models that I have information for but they use very different electrical systems and wiring diagrams. You need to tell me the model if I need to look at the wiring diagram.

Rats. I don't have information for that one. Chances are there are little or no computer controls yet to complicate the head light system unnecessarily. Using a typical wiring diagram I have etched in my mind, the way I would approach this is to find the wire that goes from the head light switch to the dimmer switch, (typically in the turn signal / multi-function switch), and connect a voltmeter to that so I could watch what happens when the lights start flashing. That would tell me which way to go from that point.

I looked at some other 2011 Kia models, and they do indeed have a very complicated computer involved with the head lights. If that applies to your model, your mechanic will need a scanner that can access those computers so he can see what commands it is seeing and responding to. That usually requires driving the vehicle with the scanner connected until the problem acts up.

Since rough roads affect this, you might want to wiggle the wiring harnesses and connectors to see if you can make the lights flash. That would identify the place to look for a bad connection or corroded connector terminal. Sorry that I don't have a better answer for this.

Keep me posted on your progress. I'm sorry that I don't have a wiring diagram I can look at, but I'll offer any suggestions that might be of value.