Intermittent mercury 115 hp 4 stroke starting problems.

[Diggers]

I have a 2017 mercury 115 4 stroke that has intermittent starting issues. We will be on the lake and shut off the engine for awhile to fish and when I try to start it it crank fine but won’t fire. When it finally does start it runs perfectly. This has been going on for more than a year. It will be fine and then just happens. It is like trying to start it with the run switch off the the switch is on. This happened a few day’s ago and I had to try over 50 in a half hour and then it finally started. Any ideas?