Very slow first Mobile Service call after one minute incativity

Question

My mobile service api (basic tire) response about 30 sec delay for the first call. The subsequent calls are fine but the first call even sometimes times out. Which is totally unacceptable. The worse is that after one minutes inactivity it stars again.
It uses SQL Server (Standard tire) which is the culprit I guess. Because if I do a manual db query before
the time lag of the api call disappear. I set up automated api calls  requesting db quires in about every minutes but did not helped. Looks like they are screened. 
What should I do until I have enough customers to get an api call every minutes?
It's a quite important issue because due to the bad user experience the app will never have enough customers.

Answer 1

I have done a lot of testing to gain more accurate data about the case. It's quite time consuming because I have to wait some minutes after each testing. I focused this time only one of my stored procedure and measured it from the app, from browser and from
VS SQL Server and turned out I was wrong there is a similar significant time lag from all method and if I wait enough about half an hour in all method the stored procedure call will time out. Thus, the underlying issue is probably in SQL Server.
The VS SQL Server provides the following error massage:
Msg 4083, Level 16, State 1, Procedure likingProbability, Line 51
The connection was recovered and rowcount in the first query is not available. Please execute another query to get a valid rowcount.
The actual rowcount in the code:
SELECT @howGood = howGood FROM goodforme.Scans WHERE itemId = @itemId AND userId = @userId
IF (@@ROWCOUNT > 0 AND (@howGood = @MAX_RATE OR @howGood = @MIN_RATE))
BEGIN
SET @howGoodPrediction = @howGood
RETURN
END
For me it looks like the rowcount should be valid. 
In the second call the response is valid but with huge delay like 20 sec, but in the subsequent calls it's linearly reduced to about 1 sec. And if the next call happens about 30 sec later the response will have increase again to about 10 sec time lag and so
on. Thank you for helping to solve the issue.