Perhaps a shock absorbing hitch would work, but I'd try redistributing the trailer load first. If the tongue weight is less than 5% of the trailer weight, increasing the tongue load might help to as much as 10%. Be sure the hitch, tongue, and pickup can handle the increased load. If you could get that tongue weight by moving the trailer axle back, that would also increase the tow stability. Moving the axle is likely awkward, but redistributing the load can help, too: for example, move tools, wing cover bags, whatever from behind the axle to ahead of the axle. Move weight that is already ahead of the axle further forward.