Bonanza 35 pilot reported an engine failure. They were preparing to land on a highway when the engine regained performance so they diverted and the engine failed again on short final.

Narrative

I departed ZZZ1 solo in Aircraft X on the way home with a planned fuel stop at ZZZ2. Approximately an hour after departing my fuel stop; ZZZ2; I began losing manifold pressure while cruising at 17500 ft. I initially assumed the throttle friction lock was loose and had pulled back. I added power to compensate and tightened the friction lock. The engine continued losing manifold pressure. After the manifold pressure had reached 25 inches; I began doing my flow and checklist for engine failure while I looked for a suitable landing site. I switched the fuel tank from the left tank to the right tank; switched the AUX (Auxiliary) fuel pump to high; and put the mixture to full rich.The manifold pressure dropped to 18 Inches before the engine quit altogether; I immediately rolled the airplane southbound; downhill; and toward ZZZ. As I descended; I squawked 7700 on the transponder and [requested priority handling] to ZZZ Center. I did not hear a response; so I transmitted it on Guard. What I believe was an Aircraft Y flight acted as a relay for me and ZZZ Center. I began heading for the best landing site in glide ratio; a highway about 10 miles north of ZZZ. As I descended; I tried everything I could to restart the engine. I played with the mixture at different settings; pumped the throttle; switched tanks; and changed the AUX fuel pump from high to low; then low to high.After reaching 8700 ft; and right before I secured the airplane for a forced landing; the engine jumped back to life. In retrospect; it was audibly running rough. I firewalled the power and climbed toward ZZZ. I started heading for a right base on Runway XX when it was within my glide ratio. I then switched com 1 to ZZZ's CTAF on XXX.X and stated I was an aircraft [that needed priority handling] heading for a right base on the runway. All was normal until the landing. I carried a small amount of power as I began rounding out. As I pulled the last bit of throttle for the flare; the engine quit a second time.I was able to roll off the runway with the energy I had. I reported to Guard that I had landed safely and corresponded on XXX.X for a tug to the FBO. The airplane was tugged into a parking spot near the FBO and secured. As I waited in the FBO; an employee informed me that the ZZZ Center wanted me to call them. I spoke with someone on the phone who informed me they had all they needed.