C208 pilot reported loss of engine power and a return to the airport.

Narrative

I acting as pilot in command; was given clearance to takeoff from Runway XX right at taxiway 1 from ZZZ tower control. My initial clearance said to fly runway heading. At approximately 4;300 feet I was given a clearance to turn direct ZZZZZ and climb to 9;000 feet. Approximately five minutes into my climb and approximately 4;700 feet MSL I started experiencing a large drop in engine performance and verified it with the torque instrument gauge. I immediately disconnected the autopilot verified my airspeed and pushed my throttle lever forward. I did not see an improvement in engine performance. I immediately ensured my fuel switches were in the on opposition; condition lever was full forward; prop lever was full forward; and attempted to push the throttle forward again. I did not get any immediate response out of the engine. I lined up with a highway to land on. I continue pushing the throttle lever back and forward again and eventually was able to get power to the engine. I [requested priority handling]; and turned back towards ZZZ airport. I requested to land on Runway XY since it was the closest runway to me. I landed without incident and taxied back to the ramp. I contacted my company flight follower and advised them what had just occurred. Emergency services came to my plane and made sure everything was OK. ZZZ airport operations also came to my airplane to get a phone number and picture of my pilot certificate.