There are phases of sleep that you pass through. Seems like you pass through the lighter ones relatively quickly and you're getting dragged awake out of a deep sleep phase.
Either give it a little bit longer (like 35-45 minutes) or try 10 minute catnaps.
There was an android app that monitored your breathing and motion when the phone is placed next to you on the bed. It claimed to wake you when you were in the right sleep cycle to wake up clear. I tried it as an alarm clockreplacements and it seemed to work...but it was years ago and I forget the app name
In 2k1 my company moved a telecommuter back inside; some management dork demanded it. He said "yeah, but I take a nap after lunch, and I'm gonna take a nap after lunch." And he did. And we all heard and envied his ability to do so.