When out I'm out fishing and when i start my boat to move to another area sometimes my main depth finder will shut off when I start the boat. It does not do it all the time.
Any suggestions what to check or look for?

check water in batteries if you have flooded cell. turn on voltage on graph and look at it before you start, check voltage setting to see what min. is.

I did an update on some birds I had and it reset the voltage setting so they shut down like yours are doing, just had to reset the voltage safe setting.

2 possibilities and it’s probably a combination of each. One could just be the battery getting weaker as the day goes on, when you start the motor, it’s taking more of the available battery and not leaving enough for the graph. Second, if you aren’t wired with big enough wire to the graph, it’ll have the same effect.

You need to make sure your battery is proper sized and make sure your graph isn’t tied into a cluster f of undersized wiring.

I agree with this.
Get the battery tested and upgrade to a Sea Clear harness!
I went with a group 31 AGM from X2

Mine use to give me a low voltage when I cranked the battery, bought the sea clear harness and imaging and electronics work amazing. Then when I added AT, I put another battery in the boat as a dedicated electronics battery. Never have had an issue, but what made the biggest difference was the sea clear harness. The twist lock they use to wire everything together is so genius and simple. I called and actually wanted to order more of these type of connectors for my duck boat and all the LED lights we wire together, they wouldn't sell me just the connectors though unfortunately.

I will check the water level in the battery this weekend and charge it to see if that makes any difference.

Thanks for the input.

Voltage drop. Now find out why the voltage is dropping. Bad battery or bad connection. Pretty simple

Concur....proven. My G3 main battery amps dropped below the amp required....took 1 year for this to happen. Basically out fishing, a few things started to happen and I never associated them with the issue.

blinking screens, horn wouldn't work, lights dim.....

Main battery was not wired to the bank charger.....charged and wired to bank charger and no more issues...2021 G3 BTW, factory lazy I guess.

It’s your voltage drop. It was happening to me every time I cranked up my main engine. The right side Helix 12 always went off.
What I did was run #10 wire straight to my cranking battery with an inline 30 amp fuse. One run per unit to the battery not both tied together. Since then neither one of my Helix 12’s at the console has flicker once.

I installed a separate battery on mine. It runs my two Helix's and the LED light strips on my rod holder when I fish at night.

By all means check the battery and connections, but don't neglect to check the wiring on this issue. You need a dedicated wire of the correct size DIRECT TO THE BATTERY. Many times when I see this issue, the graph is wired into a factory fuse box or non dedicated wire that is to small. I have had to install new wiring to my graph's on every boat I have ever owned including my latest skeeter. You would think as expensive as these boats are now they would come with the proper wiring for modern electronics, but most do not. Even the highest end boats usually do not.