Acer Z530 with a boot loop

Hello,
my ACER Z530 smartphone does not boot correctly. Since 3-4 days it has a boot loop. I do switch on the phone an see the ACER screen. After round about 30 seconds the screen switched off and it boots again.
I have done no updates in last time (but Android play store updates are activated and makes updates in background). The phone is not rooted and no custom rom is installed.
I tried to get th recover screen of phone with power on and volume up. The same I tried with power on and volume down and also both. All with and without SIM card.

Who can give a hint to:
- get the recovery mode
- break the boot loop

Thanks

Andreas