Edge 305 when you push the mode button it cuts off. can not reboot

Edge 205 or 305 often crash, then impossible to power on again.

Here is the way to reset the Garmin edge :

Soft reset : hold mode and lap/reset buttons for 10 seconds
Hard reset : device should be powered down, hold start and mode buttons for 3 seconds then pulse press the lap/reset button.

After soft reset, you need to hold start button for up to 10 secs before it starts.

After hard reset, you will loose all your data, including profiles.

Just to be sure ...

Here is the way to reset the Garmin edge :

Soft reset : hold mode and lap/reset buttons for 10 seconds
Hard reset : device should be powered down, hold start and mode buttons for 3 seconds then pulse press the lap/reset button.

After soft reset, you need to hold start button for up to 10 secs before it starts.

After hard reset, you will loose all your data, including profiles

Now if this does not work, you should check battery. Does the device charge when plugged on PC ?
If it does not, either battery is out of order or the contacts inside the device re broken. This may happen if device is used in continuous vibrating environment like mountain bike.

Changing battery or fixing contacts issue is explained there :

http://blog.mtbguru.com/2008/11/06/surgery-on-the-garmin-edge-305/

Try hard reset.

Hold mode + start for ten seconds (device off beforehand). Keep holding then pulse push lap/reset button.

You get a screen asking to return to default settings. You will loose all your data, but device should work then

Normally with Garmin sat-navs you have to switch the on/off button off and hold for around 8 seconds to reset the device

Try soft reset :
hold lap/reset and mode buttons for ten seconds, then release and wait 10sec, then hold start button for 10 seconds, device should start

maybe the lap/reset button is continuously pressed. As pressing both mode and lap/reset performs soft reset.
Make sure the lap is not dusty ...

Otherwise try hard reset holding mode and start then pulse on lap/reset. all data will be lost but it makes it start correctly

Try this first :
Hold Lap and mode for 10 seconds or more, then release and wait ten other seconds.
Then hold start button for 10 seconds, device should start.

There is a generic battery contact problem in the body of the gps, same in 305...this link will show you how to remedy it..MTBGurublog i have done it with my 305 and now do not have the shutdown anymore.... But, before you perform surgery try a full reboot... turn unit off then press mode and power together... unit will ask if you want to delete data..select yes and then manually insert all data again

Not sure to catch all you did. Apparently your battery is discharged. So you should plug your device on charging via USB. Wait for a while (1 hour) then reset the device (Hold mode and lap/reset for 10 seconds, release, then hold start for ten seconds