You may want to try turning it off, pulling the battery and leaving it out for about 5 minutes or so, then putting it back in and trying to turn it on.
If this does not work, try turning on the phone in "Safe Mode" and see if it will load. If it will, then you have something on the phone that needs to be removed (bad app, etc.,). If it won't, and still sticks at the logo screen, then you can either try a "Hard Reset", but that should not be done unless other options have been exhausted as it will wipe all your data, and/or contact the manufacturer (if the device is under warranty still) to see if they will repair/replace it.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power"...