have a echo srm210 (grey string trimmer) that starts fine and runs pretty good. late last season i noticed it started shutting off randomly when being used. most of the time it restarted right after no problem, other times id have to wait a half hour to get it started. i did a general look over and couldnt find anything wrong, brought it to the dealer. dealer left it running at idle for and hour and everything is happy. they suggested it maybe a coil but not sure until they took it apart. ive noticed it only shuts of when being used, any ideas??