Battery draining on hybrid 2005 Alphard

[Alph]

Something repeatedly draining the Battery, despite being replaced a year ago, so needs external boost charge to start when unused for a few weeks 

Interesting that when engine stopped eg mid journey, it won't restart immediately, needing 15mins rest before restarting then with no problem. Very odd. 

Any ideas welcome and recommendations for servicing it in York area appreciated

Thanks Sharon