I've had 2 srv's explode, while driving without shields, just under 90% health, at about 20 m/s (and before the last patch)
Since then I've clocked about 1000 km driving flat out on various high g worlds and no more explosions. Shields on, repair when I get below 50%, and I have been damaging it a lot. It's hard to dodge those big rocks at 55 m/s after a jump and at over 3g climbing a mountain doesn't work, you end up tumbling back down, hand brake will not stop you. I usually put my cargo hatch back up if I don't forget. I've let it sit still, have let it keep on driving in camera mode, only thing I have avoided is low g planets as I get air born too easily on those, and it takes a long time for materials to come back down!