2003 Toyota Pickup No AC Intermittently

I bought my 03 Tundra in Jun,'03 w/ 11K miles. I'm on my 3rd AC Blower Motor (replaced @ approx. 48k & 76k miles). Took to dealer for noisy blower motor @ 92k, 108k, 124k, & 128k. AC was working at the time, so they said there's no problem. Sometimes it would be noisy at start-up; other times about 30 minutes into ride. Now 3 times in the last 3 weeks the AC fan would not blow. The first time (7/15) & yesterday (8/03) it started working about 15 minutes later; the other time (7/23-24), the following morning. When the fan does come back on the AC works great. I'm wondering if I need to replace my Blower Motor again or if this sounds like some sort of relay switch issue. Has anyone out there experienced this?? - Thanks, David...