Apple logo shows on my iphone 7 then it turns off.

About 5 days ago my iphone 7 would say no service the majority of the day. There would be a few minutes when it would work. I was finally able to do the last iphone update just two days ago. After the update, my phone worked for about 10 hours but now it just has the apple logo and then it shuts off. There has been no damage to my phone.