Internet connection

I am using Siemens 4200 DSL modem on my windows XP running desktop. I hav this strange problem with internet connection using this modem.
When I start my modem and PC in the morning, the internet connection will not be established directly. The modem connects for a few seconds and then drops the connection. The internet and DSL lights on the modem goes off. After about 30 seconds it connects again and then drops again... This goes on sometimes for hours before I get a stable connection. But once I have the connection, it rarely drops on its own. Kindly hlp as it is very annoying .. I called my ISP providers technician and when he uses a Linksys modem the connection is established directly and doesn't drop!!!! He says the modem is faulty, but I have already got it replaced and I don't think the modem itself has a problem. I feel I am missing something in the settings. Please advice...