The pilot reported that the airplane's engine lost power when the airplane was about 150 feet above ground level after takeoff. He stated that after about 3 seconds the engine restarted and ran for another 6 to 7 seconds before losing power again. He elected not to land on a busy highway and selected a small field to attempt a forced landing. He realized he would not be able to make the field and elected to stall the airplane into trees. Subsequent examination of the engine confirmed engine crankshaft and valve train continuity. Each cylinder produced "thumb" compression and the magnetos produced spark at all leads when the engine was rotated by hand. Fuel was found within the fuel tank and fuel lines leading to the engine. No anomalies were found that would explain the reported loss of engine power.