Have an electric hot water heater that is ~8 yrs old. Hasn't been used much in the past few months in vacant vacation house. For the last few days we have begun using it again & have to reset (breaker off/hit reset button) 2x/day to get it to provide reliable hot water. What could be causing this? Is this a plumber call or a DIY thing?

Thanks!

some plumbers have the necessary electrical testers to troubleshoot electric water heaters.
around here electricians are the go to guy/gal.

It can be a diy project. I am betting that your bottom element is burned out and when it switches from the top element to the bottom, the short trips the breaker. Set the lower thermostat to the lowest setting and the upper to the highest and see if it trips. If it trips, it is the upper, if it continues to heat, wait till the tank starts getting hot and switch the lower element to the highest temp, and the upper to the lowest. This should pop the reset on the upper thermostat almost immediately if the bottom element is causing the short. You will need to check the information plate on the heater to make sure what type of element that you need. If you can handle all this, I or someone else can give directions on how to change the element out. You will want to buy an element rated for low watt density for the bottom element.

The lower element is probably shorted out. I assume the water is super hot when it pops out, but, you do not know it has stopped working until after you use all the hot water out of the tank.