My father-in-law bought a Timemaster earlier this year and experienced a similar problem. It would shut off whenever he would try to move forward. He called Toro and they sent out a repair company to pick it up. The repair company told him that Toro was having lots of issues with the Timemasters, especially with the safety cut-off switches. Needless to say, my father-in-law called Home Depot (where he bought it) and they agreed to let him return it and buy a different brand mower.
You might want to try the same thing with the dealer you bought yours from if you keep having issues. Good luck.
Long Reach Hedge Trimmer