Siri stops listening mid-sentence on Iphone 6 Plus 8.3

Every few days, Siri stops listening in mid sentence for all requests. I'll say Driving directions to Walmart, Siri will stop listening after a word or two. If I restart my phone, everything is fine. Any suggestions or anyone else having this issue. It's been going on for a few months. Does not have a problem with siri on the Apple Watch.

Mike