It could be the anode in your hot water heater being eaten away Or just a lot of aeration of the water system.
On many of my jobs I do install a Hoffman Air eliminator on the hot water system and this normally removes all the bubbles. Talk to your local LMP good luck
If I put it on top of the tank I use a heat sink made with a 4 elbow swing to stop the stratification of hot into cold. ( Heat goes to the absence of heat) The other place to install it is on top of the riser was that is where the bubbles accumulate. Spirovent makes a fantastic bronze and stainless steel air removal device that removes micro-bubbles from the system and this could also be used but it is costly and maybe slightly over kill
I lick to putt it on top of the hot water pip comin outo the tank an then bring the pipe near the flore to connect to the hot water pipe the air gets trapped in the loop an then the taps dont spit. That cood be wat you said.