Fight or flight.
I always win the interdiction minigame against NPCs. After you win a couple of times, the game gives you a break from them.
However, I'd look at it as an opportunity to learn some basic game mechanics.
Flight
Submit to interdiction by zeroing your speed, and as soon as you drop from supercruise, go max thrust and start boosting continuously away from your attacker.
The Cobra is pretty quick anyway, but with Class A thrusters you can just fly "a bit" evasively whilst boosting away. An upgraded power plant and distributor will give you more energy and faster boost recharge.
NPCs equip to your combat/trading level, and won't be using the kind of gear to keep up. Once you've put 5km between you and them, you can just engage frameshift and away again.
Fight
The Cobra MK3 is a good multirole ship, and does have decent weapon slots. Upgrade your power plant, distributor and shield class. Add a hull reinforcement if you have a spare slot. Add two medium multicannons and two small beam lasers - start with gimballed for autotracking. In fire control, assign beams to your secondary fire, and multicannons to primary.
When interdicted, target their ship, and decide if the fight is worth it. If the NPC is rocking a medium gunship like a Python or Fer-De-Lance then running is the better option
If they are in an Eagle, Viper, Diamondback or similar, then definitely game on. Keep your ship speed "in the blue" for maximum manuverability. Follow them round and round, strip their shields with the beams, then finish off the hull with multicannons.
That's about as easy as we can make it for you
Happy flying, commander o7
