My 2014 Nissan Frontier (4 cyl. AT) has about 78,000 miles on it. I bought it used with about 43,000 miles on it and I am the second owner. Have had no problems until recently. Occasionally now the transmission starts shifting both up and down with a pronounced jolt each shift. Turn the truck off for a few seconds and then start back up and problem solved with truck again shifting smoothly (for a few hundred more miles) and then this eventually happens again. AT fluid shows on the dipstick to be clean and at correct level. Truck has never been used hard and never has towed anything. Any thoughts on what might be going on and how to proceed would be appreciated. Thanks! Art G. from SC.