Charley is correct. What you budget for Search Ads is spread throughout a 7-day period. When you don't see impressions in the early morning hours, that could be because your allotted budget for the day has been spent. Check back around 8am Eastern US time in that case.
As you review your promotion over time, you can divide your budget for each of the 7 days your promotion runs and review your stats. You should notice that your stats are fairly consistent throughout your promotional week. If you'd like to increase the number of impressions you get on a daily basis, you can increase your weekly budget to accomplish that.
As this does not appear to be a bug but does appear to be a pertinent Site Help question, I'm going to move it to the Site Help forum section now. You'll be able to find the thread there!