Hengest,
Well hopefully you are playing in the Mobius private group (or if they can't add anymore now because they are too full just play solo to start out and later you can join Mobius private group or Open when your feeling more confident).
So are you getting blown to pieces from NPCs interdicting your or just accidents? Either way, always have enough insurance to cover yourself no matter what - unless you like risking it!

But if you are getting interdicted by the AI (an NPC) while trading it is really easy to get away. First, just submit - bring your throttle to zero (a throttle zero button is a good hotkey for controllers or Joystick/HOTAS setups as is a 75% throttle, but that is another topic). As soon as you are pulled out of supercruise and see that NPC behind you, probably saying something like, "Your cargo is mine!". Just start hitting your boost. When I'm trading I usually just fly with 2 pips in shields, 4 pips in engines, and no pips in weapons because I don't even have weapons on a trading ship. So if engines are maxed, just bob and weave, move left, right, up, roll, etc. and keep tubroing. It won't be long for FSD to be ready to use again if you submitted (I think only 5 seconds or so). Then just weave one last time and hit your jump button. You may get tagged a bit when your charging, but I find that after even a couple of boosts the AI just isn't that smart and doesn't really keep up with you.
I realize some commanders like to turn and fight, so if that is the case then you will obviously need weapons but I say still submit just to make it easier on yourself with less interdiction wear & tear damage and your FSD will charge faster. But if your dying in fights, maybe its good to just run until you can afford a good fighter (like a Viper or Cobra) that you can later outfit for some butt kicking!