Recently my ‘13 Sonata has been randomly vibrating in straight lines in the front and it happens out of nowhere. Its usually when the wheel is slightly turned to the left as well or when the road tilts on an angle 
but is still a straight line road. It happens when pressing the brakes or without pressing brakes and it also happens around 35-55mph but never high speeds or super low speed. Not sure if its something with the front suspension area as only the front of the car hops, you can also feel a thudding in the steering wheel but it doesnt shake violently at all. Its almost like the wheel just randomly hops. Tire pressures are good and the wheels aren’t bent either they’re brand new tires and wheels as well. Already had an alignment and I got the ball joints, inner and outer tie rods and the sway links changed a few months before this started due to those parts being worn. Any help is appreciated. Remember, it only happens randomly, say every 5 minutes of cruising at 40mph and then randomly stops and each shake is sometimes more violent than other times and lasts for about 5-10 seconds (Car is front whee drive)
The first thing that I would check would be the condition of the struts. More than likely, one or both of the front struts is worn-out or damaged. Please note that they should be replaced as a pair.
Have the front tires balanced as well as check the front struts. Also check for looseness in the axle shafts and condition of the suspension bushings.
Need to check if something was left loose. A loose lock nut on a tie rod for example can cause a mild shake while driving straight but drive normal most of the time.
Forgot to give a follow up but the problem was the outer tie rods. I gave a shop inner and outer tie rods to change and it turns out they cross threaded one of the tie rods causing the nut to be held on by like 3 threads so when i drove the wheel was turning outward when accelerating and inward when braking. Note to self: dont let anyone touch your car no matter how lazy you are lol
Also ended up changing both strut assembly completely as one was bent and worn, and the other had a bent mount
When it rains it pours, hope all is good now.