Welcome to Android Forums, makhluktuhan.
It's possible that you've got one 3rd party app (downloaded from Android Market, perhaps??) which is supported by a background "service" which may be interfering with other apps or widgets, syncing apps/widgets in particular are vulnerable.
This is why rebooting the device often temporarily fixes the issue, but it'll likely return as the service cycles and restarts.
To troubleshoot, begin by going into all syncing apps and widgets such as Gmail, Facebook, weather, news, etc and configure them to sync on demand manually rather than autosync.
If doing that fixes the issue, go one by one and reinstate autosyncing and use the device for a while, adding each app or widget until the problem shows up again.. then you've identified the rogue app or widget and you can either leave it at manual syncing or just disable it and try another version of that app from Market.
It can be time consuming, but worth it in the long run.