Message failed to send

When I restart my iphone 6 Plus, I have a red exclamation point on my messages app. It disappears and then I get - The Message to .........failed to send.

I am also experiencing texts flashing on my screen but when I go into the messages app they are not there. I have to shut down and restart the iphone for them to download. I am at a loss what could be happening and can't get any support from Apple.

Thanks