An update. took a short trip for coffee yesterday morning, came out and engine would not start. After about an hour, it started. This time the check engine light came on, and a diagnostic check does reveal a CPS problem. I've got one on order ($50 w/shipping). My neighbor who is a Mercedes tech checked the parts price at his work and it was over $200. Thanks for everyone's help. I still plan to check the solder points also, just in case.