Strange jolts while driving

[dra2650]

2005 Maxima 180K-ish miles

I bought this car about 6 months ago. Drove the car on it's first road trip about 5 months ago. After several hrs, at hwy speed the cruise would disengage. It did the same thing on the next road trip about a month later. I can't with any confidence say if the cruise continued to not work or would drop out.

This past week I took another long trip. The cruise dropped out after about 3 hrs driving, but I could re-engage it. At about 250 miles, the cruise dropped out again and I opted for manual (foot) control. Now the more troublesome problem (and probably related) started. The car would "shutter" one time. By shutter I mean that the car would for one "snap of the finger" decelerate with a "jolt-like" bump then continue. These shutters are sporadic. Secs to mins apart. More than not, 5-10 mins apart. Most times in singles, sometimes in pairs, or less frequently in triplets (only once that I could remember). The triplet was at acceleration from an almost stop, but that was the only time at any speed below 60mph.

The next morning I drove for about 1 hr at hwy speeds (cruise on and off) with no issues.

The next day the trip resumed. The problem repeated at about 250-300 miles (cruise dropped out, then the shutters started).
Each day (with 2 days in between that included only 20 - 30 miles of local driving each day with no issues) the total miles driven was approx. 500 miles.

When the shutters occur there is no drop or surge of RPMs on the tach. Transmission? Fuel pump? Heat sounds like the root cause.

Thanks for any ideas,
David