Android : Lock screen activity takes seconds to appear

I have an app that makes use of a lock screen widget. Once clicked, a new activity is displayed to the user. My is issue is about the time required to fully display the activity. Sometimes it takes a few milliseconds and sometimes up to 5 seconds between the time where I click on the widget and the instant where I see the activity.

I was thinking the issue is related to the content I put in the onCreate method but the issue also occurs with a blank activity. After some tracing it seems the extra time depends of some Android internal.

Is it a known problem? Does someone knows a workaround to start the activity quickly (eg. a flag for caching something)?