We purchasede a used Huskee Hydrostatic (one of the 690 models) riding mower a month ago. When we looked at it initially it started right up - and did so the next two times we used it. Since then, when you turn the key it sounds like it wants to start, but the part under the hood you can see that the rotating screen won't turn - almost like it is locked up. Then, if you let it sit a while and try it again, it starts. Very frustrating. Battery is new and charged, seems to have fuel in the line/filter. Once the machine has been used and is warm, it will start right away. Any ideas, before I pull my hair out??