2007 hino 268 airbrakes problem


New Recruit
Can someone tell me what's causing my truck not to start after I turn it off? 2007 hino 286. When I park for a long time, from 1hr above, it will start normally.but when I turn off the engine and try to start again in less than an hour, it won't start. Then I'll have to release all the air in the parking brake, wait for an hour, before it starts again. What could be the issue ? I've taken it to about 4 mechanics, spent a lot of money, but no one has been able to fix the issue.